A TREATISE 
DESCRIBING THE 
Process of Coating Tablets and Pills 
AND OF 
Manufacturing Pulverous Pills 
and Globules 
By Francis J. Stokes \ 
PHILADELPHIA 
Copyrighted 
THIS WORK IS DEDICATED BY THE AUTHOR TO HIS MANY FRIENDS 
IN THE PHARMACEUTICAL INDUSTRY, WHOSE KINDLY 
AND GENEROUS ASSISTANCE IS HEREBY 
ACKNOWLEDGED QV 
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'Y Tablet and Pill Coating 
The process of coating tablets and pills has been surrounded with 
more or less secrecy and has in consequence been considered by those 
unfamiliar with it as quite difficult. It is in reality quite simple and 
can be mastered by anyone who uses ordinary judgment and common 
sense. The following instructions should be ample after a little experi- 
menting, to enable anyone to undertake the work with assurance of 
success. There are several fundamentals to bear in mind which are 
set forth in the paragraph headed—GENERAL PRECAUTIONS. 
Tablets were formerly coated by what is called the hot process, 
that is to say, they were placed in a revolving coating pan which had 
copper steam coils wound around the outside of the pan. This heated 
the pan and accelerated the drying of the syrup as it was applied to 
the tablets. A considerable portion of the syrup dried in a hard layer 
on the surface of the pan and was difficult to recover or was lost. 
It was later discovered, by blowing air upon the tablets, the drying 
took place about as rapidly, and little syrup was deposited on the sur- 
face of the pan. As a result the cold process, as it is termed, is now 
very generally used. In some cases warm air is used, which increases 
the rapidity of the drying. Warm air is not necessary, however, and 
many manufacturers use cold air rather than incur the expense of a 
heating box for heating the air. Steam heated pans are preferred 
by some for sugar coating those compounds such as contain bromides 
and other drugs which absorb moisture rapidly. 
EQUIPMENT—The equipment of a coating department includes 
one or more coating pans, polishing pans, a fan blower, a syrup kettle 
or cooker, glass graduates, stirring rods, scales, dippers, workbench, 
drying closet, screens and containers for the stock solutions and 
powders. 
COATING PANS—These can be of copper or galvanized iron, 
the former being preferred on account of their shape. The galvan- 
ized iron pans have corners where the sections are fastened together, 
in which the tablets are apt to stick, and their rolling action is not 
quite as satisfactory as in the copper pans. The size of the pan 
depends on the quantity of tablets to be coated at an operation. Usu- 
3 ally a number of pans are used so different lots of tablets can be 
coated simultaneously in various colors. The most popular sizes of 
coating pans are those having a diameter of 24", 30" and 36". The 
capacity of the pan depends on the size of the tablets and the thick- 
ness of the coating. When the uncoated tablets are first placed in 
the pan, they may seem small in comparison to its size, but when the 
coating has been finished, the volume of the tablets will be greatly 
increased. This should not be overlooked when starting to coat. In 
the table below is given the maximum capacity in one-, three- and five- 
grain tablets. 
f*an One Grain Three Grain Five Grain 
24" diameter 100,000 70,000 50,000 
30" “ 150,000 125,000 100,000 
36" “ 250,000 200,000 150,000 
POLISHING MACHINES—One or more of the coating pans 
may be used as a polishing machine, or as is usually the case, a special 
machine like the Polisher illustrated on page 16, which has a canvas 
COATING PAN POLISHER 
lining, is preferred. If a coating pan is used, it is lined generally 
with canvas. The canvas is cut so as to fit the pan and glued 
to it. As a coating pan is more expensive than a polishing machine, 
and as the labor involved in adapting the former for polishing is con- 
siderable, it is obvious that it is more economical to have a separate 
polishing machine or machines. One polisher is required for polish- 
ing white coatings, and can be used for no other color, as chocolate 
4 COPPER COATING PAN 
Copper coating pans are made in diameters from 24 in. to 48 in. 
the usual size being 24 in., 30 in. and 36 in. They are beaten from 
thick copper and are made very deep and so will carry a heavy load. 
1 hese pans can also be equipped with steam heating coils. 
5 6 and colored coatings stain the canvas lining, which would come off 
and discolor subsequent lots of white tablets. For the same reason 
one polisher is kept exclusively for chocolate coating and a third 
for polishing the various pink, blue, green and yellow colors. As the 
polishing process requires only a relatively short time, as compared to 
the actual coating process, three polishing machines will handle the 
output from many coating pans. An inexpensive arrangement which 
is satisfactory for small production, is to insert into the mouth of a 
coating pan a cylindrical container (see page 4), so shaped that 
it wedges in the opening of the pan. These can be made of galvanized 
iron and lined with canvas. Several of these can be had at small 
expense, and a coating pan can be immediately converted into a pol- 
isher by inserting one into the pan. 
FAN BLOWERS The standard type of fan blower of sufficient 
size to supply an air blast to the pans is required. I recommend a 
15 Blower for one pan and an 18r/ Blower for three or four pans. 
1 his fan can be placed on the floor, or hung from the ceiling. A line 
of tin or galvanized iron piping of a size to fit the outlet of the blower 
is extended along the ceiling over the pans, and from this smaller 
pipes are extended down to the mouth of each pan. These drop pipes 
should be fitted with a damper so the air blast can be controlled, and 
a loose spout which can be removed when emptying the pan. The 
illustration on page 6 shows this arrangement of the pipes in 
relation to the pan. The standard gutter spouting with elbows and 
fittings as supplied by tinsmiths can be used. As stated above, some 
coaters prefer to blow warm air to hasten the drying, especially in 
humid weather. For heating, a steam coil or gas heater is placed in 
a closet and the suction inlet of the blower connected with the closet, 
which will meet all requirements. 
COOKING APPARATUS—The stock gelatine solution and the 
syrup solution used for sugar coating tablets require heat in their 
preparation and application. A small steam jacketed copper kettle of 
three to five gallons capacity is very satisfactory for this purpose. A 
gas stove on the work-bench with suitable agate double-boilers will 
answer, however. The steam jacketed kettles or gas heaters should 
be conveniently situated, so the operator, when dipping out his solu- 
tions will not have to carry them far to the coating pans. The work- 
bench should be facing the pans, and with a suitable aisle between it 
and the pans. This makes a convenient arrangement. A drying closet 
will be found of great convenience for drying the tablets before they 
are placed in the coating pan, and also for drying those combinations 
referred to above which absorb moisture. A mortar and pestle are 
7 convenient for preparing colored solutions, and should be a part of 
the equipment, together with pint and quart measures and glass stir- 
ring rods. The equipment is complete with a set of perforated sieves 
for separating the different sizes of tablets which may be coated in the 
same pan, at the same time for convenience and also for screening out 
broken tablets. 
PREPARATION OF STOCK SOLUTIONS AND SUB- 
COATING POWDERS—Before the operator can commence to coat, 
he will have to prepare his gelatine solution for the under or sub- 
coating, and make his starch and sugar mixture, which is dusted on 
when forming the under or sub-coating. He will also have to prepare 
his syrup solution and his stock colors for coloring the syrup. The 
following formulae for these various solutions and powders have been 
found to give very satisfactory results. They are susceptible, however, 
of considerable variation, and the operator may decide to modify the 
formulae to suit his own ideas after he has become experienced. I 
find rarely two coaters who use exactly the same formulae. 
GELATINE SOLUTION FOR SUB-COATING is prepared 
by dissolving two pounds of powdered or granulated gelatine and 
twenty-four pounds of granulated sugar in two gallons of warm 
water, mix thoroughly and bring to a slow boil. When thoroughly 
dissolved strain and put in a can or crock. Some coaters add to the 
above mixture twenty-four ounces of powdered acacia. This is not 
necessary, however, and the solution is stickier and harder to handle 
than without the acacia. The gelatine solution will gelatinize when 
cold, but will always go back into solution when heated, and should 
always be applied hot. 
WHITE DUSTING POWDER, which is used in connection 
with the gelatine solution for sub-coating is a mixture of thirty-six 
pounds of powdered sugar and twelve pounds of powdered starch, 
mixed thoroughly and screened through a thirty-six-mesh sieve. Some 
coaters prefer to add two' pounds of powdered talcum and two pounds 
of powdered acacia to the above. The talcum assists materially in 
producing a smooth sub-coating. 
CHOCOLATE DUSTING POWDER, which is used for sub- 
coating chocolate-coated tablets, is the same as white dusting powder 
with addition of six pounds of powdered cocoa or powdered extract 
of chocolate. This dusting powder is screened in the same manner 
as the white. The dusting powders, or stock powders, as they are 
called, can be stored in galvanized or other suitable containers. 
8 SYRUP used for coating after the sub-coating has been applied 
is composed of thirty pounds of granulated sugar dissolved in three 
gallons of water and brought approximately to the boiling point. The 
syrup is then strained through cheese-cloth and when cool is ready 
to use. This syrup is used in this form for coating white coated tablets. 
It is applied cold in all cases. 
COLORING SOLUTIONS FOR SYRUP—If the coating of the 
tablets is to be colored, the syrup is tinted by adding to it aniline color 
prepared in the following manner: One ounce of powdered aniline 
is dissolved in one pint of hot water. These solutions which are 
afterward referred to as stock solutions’, are usually prepared at first, 
and stored in separate bottles and kept ready for use. 
CHOCOLATE COLORED SYRUP—This requires no previous 
preparation, as all that is required is to mix twelve ounces of choco- 
late-brown paste with one gallon of syrup, which is applied without 
further dilution. Some coaters, however, prefer to prepare a chocolate 
coloring mixture with which they color their syrup. The formulae 
is to mix one pound of chocolate-brown paste in three pints of hot 
syrup. This is stored in a wide-mouth stoppered container, and 
diluted in the proportion of four ounces to the gallon of syrup when 
applying the coating. 
WAX SOLUTION used for polishing is made by dissolving one 
ounce of carnauba wax in one pint of acetone. Beeswax may be used, 
or preferably a mixture of one part carnauba to three parts bees- 
wax. As beeswax, however, is frequently adulterated with paraffin, 
the oil from the paraffin gives trouble, and it is probably safer to use 
pure carnauba, unless the composition of the beeswax is known. 
TABLETS—These should be compressed with high convex faces 
and with as thin an edge as possible, and at the same time conform 
to good proportions. Tablet punches are usually made with three 
degrees of concaved faces, called standard, deep, and extra-deep con- 
cave. The deep concave is a good one to adopt for all purposes, as it 
forms a satisfactory shape for either coated or uncoated tablets. The 
thinner the edge of the tablet the easier it is to cover it and the corners 
with the coating. The tablets should be screened to remove all broken 
ones, as well as dust, before placing in the coating pans. 
GENERAL DESCRIPTION OF THE PR.OCESS—Before tak- 
ing up in detail the various steps in it will possibly give 
the beginner a better idea of what he is trying to do by briefly explain- 
ing the process. The tablets, after cleaning and removing defective ones, 
9 are placed in the coating pan and subjected to three to five sub-coats, 
depending on the tablets. Each sub-coat consists first of wetting the 
tablets with the gelatine solution and when partially dry sprinkling with 
a dusting powder. By this means the tablets are rapidly filled out and 
rounded up. Following the sub-coating the tablets are given sufficient 
applications of syrup to give them a hard, smooth finish, the last two or 
three syrup coats, which are known as the finishing coats, receiving 
special attention. The tablets are then polished with the wax solution. 
It is easier to coat tablets white than in any other color. Only a 
few syrup coats are required if the sub-coating has been properly done. 
Chocolate coating can be quickly done, as it also requires only a few 
syrup coats. Chocolate coating, however, may give the beginner some 
trouble to keep his colors uniform. This may occur if the finishing 
coats are allowed to dry too quickly. Colored coatings other than choco- 
late require a longer time to coat, due to the fact that the tint has to be 
obtained by slow degrees. 
After the beginner has become familiar with the technique of coat- 
ing he will find it economical to coat two or possibly three sizes of 
tablets in the same pan at one operation. It is obvious that this can only 
be done where the tablets have sufficient difference in their size to 
permit their separation by screening after they are coated. When this 
practice is followed it is advisable to sub-coat the different formulas or 
batches separately, and then syrup coat them together in the one pan. 
There are two reasons for sub-coating separately. One is to prevent 
the transfer of odor or powder from one formula to the other. The 
other is that where large and small size tablets are sub-coated together 
the small tablets are apt to stick to the larger tablets. This tendency is 
greater in the sub-coating, due to the heavier gelatine solution which 
is used, than with the syrup coating. 
The formulae given above and the detailed instructions which 
follow are the best practice so far obtained. They no doubt can be 
modified to advantage in special cases, as well as improved, and the 
intelligent coater should always endeavor to simplify his work wherever 
possible, if by so doing he can produce a satisfactory result. 
As an illustration, and to better explain the processes, let us assume 
that we are chocolate coating 70,000 three-grain cascara sagrada tablets. 
Use a 24" diameter coating pan if available, as it will be easier for the 
beginner to start with a pan which is in proportion to the size of the 
batch. A 30" diameter coating pan can, of course, be used. It is difficult, 
however, to coat a. very small quantity of tablets in a large pan, as they 
will have an increased tendency to stick to the pan after each application 
of gelatine solution and syrup, and require more stirring to overcome 
this and to prevent their sliding before they commence to roll properly. 
10 While the beginner will of necessity have to start with a clean pan, 
he will find later on that the sub-coating can be accomplished more read- 
ily by placing his tablets in a pan which is slightly encrusted with syrup 
from a previous coating. The reason is that the tablets, when moistened 
with the gelatine solution, will slide as one mass rather than roll and 
they will require much more stirring by hand to break up the mass and 
start them rolling. 
SUB-COATING—When the tablets are placed in the pan, have 
the gelatine solution for sub-coating warm and conveniently located. 
Dip out one pint in an agate measure and have a scoop full of chocolate 
powder at hand. As the tablets revolve, pour the gelatine solution over 
the tablets, stirring them with the hand to distribute the solution keep 
stirring to make the tablets roll if possible, and when the gelatine has 
partially dried and is tacky, sprinkle on the chocolate dusting powder 
until there are no wet tablets showing. The chocolate powder can be 
sprinkled on by hand, and wet areas in the tablets can be sprinkled as 
they appear. The tablets will begin to roll freely as soon as the powder 
is dusted on. Avoid using an excess quantity of powder, as this will 
roll in the pan and affect the smoothness of the succeeding coat. Should 
excess powder accumulate it will appear at the back of the pan and by 
scooping a few tablets from the front the powder and tablets at the back 
can be scooped out and separated, the tablets being put back in the pan. 
After the chocolate powder has been applied and taken up with the 
tablets, and not before, turn on the air blast until the coating is perfectly 
dry. This requires about fifteen minutes. The operator can test for 
dryness by scraping with his finger-nail or knife to see if it will powder 
off. Sometimes the tablets split or cap during the first sub-coating, and 
there are always a few tablets which stick together. It is advisable to 
rescreen tablets to insure the removal of such before applying the second 
sub-coating. Three or possibly four coats are applied to complete the 
sub, or under, coating. This sub-coating is very important, as upon it 
largely depends the smoothness of the finished tablets. 
SYRUP COATING—After the tablets have been sub-coated, the 
chocolate syrup is applied. It is advisable to again screen the tablets 
to remove the broken ones, and if the pan is too rough from encrusta- 
tion of sub-coating, wash it out. The color of the chocolate sub-coating 
will be much lighter than the color of the finished tablets. Fewer coats 
of the chocolate syrup will be required if the tablets are first given two 
small coats of chocolate syrup, having a double quantity of chocolate 
brown paste to intensify the color. Mix a pint of this intensified color- 
ing syrup and apply it in two doses. It is difficult to state the exact 
amount of syrup a given quantity of tablets will take up; I should say 
about one pint would be the proper quantity for each application of 
11 syrup to the quantity of tablets under consideration. The quantity of 
syrup, however, should be as much as the tablets will take up and not 
form into a mass so they do not roll. Pour this over the tablets as they 
revolve, distributing it as much as possible while pouring, and at the 
same time stirring with the hand until the syrup is evenly mixed and 
the tablets are rolling freely. Do not turn on the air blast until the 
tablets roll freely, and then blow air until dry, requiring approximately 
twenty minutes. There should be a distinct improvement in the smooth- 
ness of the coating after the first application of the chocolate syrup is 
added, and this improvement will become more pronounced as the appli- 
cations are continued. After two coats of the darkened syrup, the 
operator can proceed with the standard chocolate syrup, applying as 
many coats as are needed to properly round the tablets, so the edges 
and corners are smooth and show a uniform color. From five to ten 
coats may be required to produce the necessary finish. If pin holes 
appear in the coating they can be filled in by allowing the syrup to dry 
more slowly, the theory being, the longer the coating remains in a plastic 
condition the more working it will receive by the rolling action of the 
tablets. The operator can tell from time to time how his tablets are 
smoothing up by breathing on a few held in the hand close to the mouth. 
This test reproduces the color and luster which will be obtained after 
they are polished with the wax solution. If the tablets do not show up 
smooth and polished when so tested, probably no amount of polishing 
will materially improve their appearance. This practice of breathing 
on the tablets is unquestionably to be condemned from a hygienic stand- 
point, but there seems no other way for the beginner to get a quick 
line on his results. 
FINISHING—The tablets are now ready for finishing. If the pan 
is rough it should be washed out and dried. Give the tablets a light 
application—say, three or four ounces—of chocolate syrup, with the 
color, however, cut down two-thirds in quantity. The chocolate paste 
does not enter into solution with the syrup, as is the case with the aniline 
colors, and by reducing the amount of the chocolate brown paste in the 
three finishing coats, a harder surface is produced which takes a better 
polish. These finishing coats should be allowed to dry without the air 
blast. On the third or last coat, just before the tablets are dry, stop 
the pan and cover the opening with a cloth. By doing this the tablets 
will dry more slowly and retain a better and more uniform color than 
if they were revolved. It will be well to turn the coating pan a half 
revolution by hand from time to time to expose a fresh surface of the 
tablets. If this is not done, those tablets which are on top will dry a 
lighter color than those below. It will take about two hours to dry the 
tablets in a stationary basin. The operator may be able to use an air 
12 blast for the final drying, but the pan must be stationary, except when 
revolved by hand in order to expose a fresh surface. This is a danger- 
ous experiment, as it is liable to produce uneven colors. 
POLISHING—The tablets should now be ready for polishing and 
are transferred to a polishing pan. While revolving in the polisher, 
pour two ounces of wax solution over the tablets. A wide-mouth bottle 
with a shaker top makes a good container for the wax solution. Two 
or three shakes of the solution should be sufficient. Stir the tablets with 
the hand in order to distribute the solution thoroughly through the 
tablets. Allow the tablets to revolve until the acetone has evaporated 
and then dust on from a shaker a small amount of talcum powder. 
The talcum is usually applied with the ordinary commercial shaker 
talcum box, and only two or three shakes are necessary. The luster, or 
polish, should appear immediately. It may be improved by a second or 
possibly a third application of wax solution and talcum. Leave the 
tablets in the polisher for fifteen or twenty minutes, or longer if desired. 
When removed from the polisher the tablets should be spread on trays 
and dried before placing in their containers. 
WHITE COATING—Tablets are white coated in the same way 
as they are chocolate coated with the exception that white dusting 
powder is used in place of the chocolate dusting powder when sub- 
coating. Plain syrup is used for the coating and finishing. Some coaters, 
in order to get quick results by producing the number of applications of 
syrup, load their syrup by mixing with it an additional quantity of 
powdered sugar. This sugar does not enter into solution and the mix- 
ture is made just as heavy as it is possible to pour and distribute over 
the tablets. By controlling the air blast this coating can be made smooth, 
and the finishing coats will be applied, using the standard syrup. 
COLORED COATINGS—When tablets are to be coated blue, 
green, yellow or red, the same general method applies as described. The 
sub-coating is applied with white dusting powder, and syrup for coating 
and finishing is tinted with the proper coloring solution, the tint being 
intensified as the coating progresses. In other words, the first two or 
three coats are made by applying syrup of a light tint, the next three 
coats with syrup of a darker tint, and so on to the end. If the operator 
attempted to apply syrup tinted to the finished color from the begin- 
ning, the result would be a blotchy color, probably due to the fact that 
the sub-coating being absorbent would take up the color unevenly. As 
an example, take 100,000 one-grain tablets of strychnine and coat them 
red. Use a 24" pan, and after the tablets have been sub-coated white 
apply a syrup which has been colored in the proportion of one ounce of 
13 stock red coloring solution to one gallon of syrup. Give the tablets 
two or three coats and then intensify the tint of the syrup by adding 
more red in the proportion of two ounces of stock color to the gallon 
of syrup. After several coats the color is again intensified by again 
doubling the proportion of color in the syrup. Always keep some sample 
tablets of the proper color before you as a sample to match. With a 
little experience the operator can intensify the color of his syrup by 
judging its color with his eye and without resorting to measuring the 
exact proportion. When the desired shade and finish have been obtained 
the air blast should be taken off and the tablets given three or four 
doses of colored syrup in the manner described for chocolate coating. 
The pan should be stopped just before the final coat is dry, the opening 
covered and the pan turned by hand from time to time, as explained 
above. The method for coating tablets in other colors is identical. 
SPECIAL TREATMENT FOR COATING TABLETS 
WHICH ABSORB MOISTURE—Some tablets, owing to their con- 
tents, require greater care in coating to prevent the water in the gelatine 
solution penetrating the tablet rather than evaporating. It is obvious 
that such a result would prove disastrous, as this moisture, no matter 
how well the finished coating appeared on the outside, would eventually 
work out through the coating, discoloring it and producing a sorry 
result. It is therefore very essential that when coating sodium salycilate, 
mixed treatment, and those combinations containing iodides, bromides 
and other compounds having an affinity for water, care must be exer- 
cised to prevent the water “drying in.” There are several methods in 
use. A small amount of oil applied to the outside of the tablets before 
applying the gelatine solution is one method. Too much oil must not 
be used or it will discolor the coating. If a dough is made by adding 
sufficient starch to a tablespoonful of raw linseed oil and the dough 
kneaded into a ball, and the ball allowed to roll with the tablets, they 
will absorb the oil from the dough. The ball will shortly break down 
and the powdered starch, after the oil has been absorbed by the tablets, 
will appear in the back of the pan. After this preparation the tablets 
can be sub-coated in the regular way. Another method is to apply the 
stock gelatine solution, but in place of the stock dusting powder to apply 
powdered calcined magnesia. It is advisable to apply an excess of this 
to be sure of absorbing the moisture in the gelatine solution. Another 
method which is similar to the above is to substitute powdered acacia 
as a dusting powder after the gelatine solution has been applied. When 
the three or four sub-coatings have been applied, the tablets should be 
dropped in trays of hot powdered starch and dried out for a few hours. 
The application of the coating can then proceed as usual. The important 
thing is to have the tablets dry at the start and also to dry them thor- 
14 GALVANIZED IRON COATING PAN 
Some varieties of pills and tablets can be handled in galvanized 
iron pans. They cost somewhat less and can frequently be used espe- 
cially for cold process coating. 
Standard sizes, 24 in., 30 in. and 36 in. 
15 POLISHING MACHINE 
The machine illustrated here is used for polishing or finishing- 
sugar and chocolate coatings. The drum is made with a canvas body 
which can be easily removed. The canvas carries and transmits the 
wax nicely and yields slightly as the tablets roll, and does not chip off 
the coating. It is much more satisfactory than the metal polisher. 
The heads are 30 in. in diameter and 14 in. deep. They will fit the 
coating pan stands (page 5) and can be used interchangeably. 
16 (Highly after sub-coating to eliminate any moisture which may have 
dried in. 
RE-COATING TABLETS—While it is not anticipated the oper- 
ator will have bad luck, this may occur now and then, and it will be 
necessary to re-coat the tablets in order to save them. Place the tablets 
in a dishpan and cover with water, stirring them with the hand until 
the edges of the tablets begin to appear. Pour off the water and cover 
the tablets with denatured alcohol to absorb the water. Drain off the 
alcohol and shake the tablets well in a sieve to remove the alcohol, then 
put in the coating pan and revolve with air blast. When dry they can be 
re-coated. It may be that the tablets will wash off irregularly and some 
will be larger than others. If this is noticeable, remove the larger 
tablets by screening and rewash them in water to reduce their size, or 
place the smaller ones in the coating pan and give them an extra coat 
to bring up to the size of the larger tablets. 
TIME REQUIRED FOR COATING—This obviously depends 
on the skill of the operator; as the skill in applying the sub-coating 
increases few syrup coats are required. It is also obvious that if the 
operator is able to load his syrup with free powdered sugar, the coatings 
will build up more rapidly and fewer be required. I know of some 
coaters who turn out a batch of the ordinary run of tablets in five hours, 
while others require a day or possibly more. Speed in coating, however, 
is not the chief end to be gained; the operator should rather be sure 
that his coatings are permanent, will not break off and will not dis- 
color due to moisture in the tablets working out through the coating. 
GENERAL PRECAUTIONS—Be sure each coat is perfectly 
dry before putting on another application, whether it be sub-coating 
or syrup, as the moisture will dry in and the result will be a cracked or 
discolored coating. Always screen the tablets after the first two appli- 
cations of sub-coating to remove broken tablets. If these are not 
removed they will stick to the tablets and produce an unsatisfactory 
result. When the coating pan gets rough inside from too much syrup 
drying on it, wash it out and the tablets will coat up much better. When 
making white coating, keep away from chocolate coating, as the dust 
will fly from one pan to another and the white coating will be specked. 
Be sure the hands are clean and not stained with chocolate or other 
colors. 
SUGARLESS COATING, which is recommended for tablets or 
pills distributed in tropical climates, is made by applying gelatine solu- 
tion in place of syrup. The process is quite similar to that of sub-coat- 
ing, in that a dry powder of chalk or starch is added to the tablets 
17 after they have received an application of gelatine solution. The dust- 
ing powder should contain some powdered gum tragacanth. The coat- 
ing is finished with several applications of gelatine solution alone. This 
coating cannot be polished with wax, but after the tablets have been 
allowed to roll in the pan for a few hours a very high luster can be 
obtained by giving the tablets a coat of very thin solution of balsam 
tolu. Wood alcohol can be used as a thinner. 
METHOD OF MAKING PULVEROUS PlLLS—These are 
made in a standard coating pan. No heat is required. As starters, either 
rape seed or sugar granules, which are sometimes known as imperials 
by confectioners, and are identical with the small granules used by 
homeopathic pharmacists, are used. Of the two kinds of centers or 
starters, rape seed is frequently preferred, as it becomes indistinguish- 
able from the pill when made. The sugar granule, on the other hand, 
can usually be detected when the pill is broken open. 
The starters are placed in the pan and an application of white 
paraffin oil is added; the powdered drug is then sifted or sprinkled 
onto the oiled centers as they revolve. The powder adheres to the 
centers and successive applications of oil and powdered drug are added 
until the pills are built up to the desired size. It is necessary during the 
process to remove the pills from time to time and screen out the larger 
ones, putting back the smaller in the pan until they are all brought up to 
an even size. When the pills are built up to the proper size the oil can 
be removed by placing them in a drying closet on absorbent paper which 
will absorb the oil as it sweats out. Some manufacturers prefer to 
remove the oil by placing the pills in a bath of tetrachloride of carbon, 
which dissolves the oil. Pulverous pills can be sugar or chocolate coated 
in the usual manner. The equipment consists of a standard coating pan 
and an assortment of perforated zinc screens. For the extensive pro- 
duction of pulverous pills special wooden tubs, four or five feet in 
diameter, are used in place of the standard coating pan. These tubs are 
mounted on the regular coating pan frame. 
METHOD FOR PREPARING HOMEOPATHIC GLOB- 
ULES OR GRANULES—PIace five pounds of XXXX sugar on a 24" 
copper coating pan, having steam coils for heating. A hot-air blast, 
however, could be used successfully in place of the steam coil. To the 
sugar add slowly a hot syrup of about 35 degrees density. This syrup 
can be approximated by dissolving two pounds of sugar in one pint of 
boiling water. 
The syrup is slowly added to the powdered sugar as it revolves in 
the pan until the globules start to form. If too much syrup is added 
18 large globules will form instead of small ones; the small ones are the 
more difficult to produce. Alternate applications of powdered sugar 
and syrup are added as the globules form and dry out. It will be neces- 
sary to remove the larger globules by screening, the small globules 
being put back in the coating pan. Those of the correct size arq set 
aside on a tray for further drying, and those which are too large melted 
down into syrup. 
The operator will have to keep stirring the sugar in order to break 
it up and to separate the globules as they form. The formation of too 
large granules can be overcome by adding less syrup or making it 
slightly lighter in density. 
19