can be obtained. Probably the best way would be to put
the ingredients into capsules, separating the acid from the
exalgine by the phenacetin and cocaine, if the mixture is to
be used internally.
This makes a mixture which is very thick at first, but yet
can be poured. Allow it to stand for half an hour and it
solidifies; by the end of twelve hours it is so firm that it can-
not be shaken in the bottle. Even if only one half of the
amount of magnesia is used the mixture will solidify so that
it cannot be shaken up if allowed to stand undisturbed for a
day or two. By vigorous shaking several times the mass can
be broken up so that it can be poured. Magnesium oxide
takes up water to form the gelatinous magnesium hydrate.
The alkalies all tend to prevent the precipitation of the resin-
ous matter in the tincture by the water.
Several chemical reactions will take place, depending
upon the order of mixing. The possible reactions are as fol-
lows: I. Ferric iron is reduced to ferrous iron, giving at first
a red solution of ferric thiosulphate. 2. The hydrochloric acid
of the tincture reacts with the thiosulphate, forming sodium
chloride, sulphurous acid, and sulphur. 3. With potassium
chlorate, the sulphurous acid thus formed gives potassium
sulphate, hydrochloric and sulphuric acids. 4. Hydrochloric
2o6 INCOMPATIBILITIES IN PRESCRIPTIONS,
acid with potassium chlorate gives potassium chloride, water,
chlorine, and several oxides of chlorine. 5. The chlorine thus
formed oxidizes the reduced ferric salt back to the ferric con-
dition and oxidizes the hyposulphite to a sulphate.
There is not enough water to dissolve all of the chlorate,
and after the reactions have taken place there is not enough
acid to form a normal ferric salt of all of the iron; a part of
it remains as an insoluble oxychloride.
Quinine sulphate and hydrobromic acid give a slight greenish
color. By hydrobromic acid a part of the mercurous chloride
is reduced to metallic mercury, and a part is oxidized to mercmic
chloride, which is much more active than calomel By adding
the calomel last the reaction can be prevented to some extent,
and the amount of mercuric chloride formed is probably not
dangerous. The directions are: Mix and divide into 10 equal
parts and put into gelatin capsules. Label: One capsule to
be taken every three hoiurs.
Conmierdal dilute hydrocyanic acid usually contains some
free sulphuric or hydrochloric acid, which has been added to
preserve the hydrocyanic acid. If one of these mineral acids
is present an effervescence will take place. Hydrocyanic
add itself does not decompose carbonates (Prescott and
Johnson's Qualitative Chemical Analysis, 4th ed., 308).
Hydrocyanic acid easily decomposes in water, but in an
alkaline solution its decomposition is much quicker, giving
a formate and a dark-colored predpitate containing para-
INCOMPATIBIUTIES IN PRESCRIPTIONS. 207
Triturating salol and monobromated camphor together
produces a liquid. But if the acetanilide and salol are
rubbed together first and then the camphor added a damp
powder is obtained. If about fifteen grains of powdered soap
are then added and a little drying powder if necessary, a mass
can be made, the pills becoming hard in an hour or two.
The order of mixing these ingredients makes a difference
in the products first formed, but after standing the results
are probaWy similar. If the solution of zinc chloride and the
lime water are mixed a white precipitate of zinc hydroxide is
formed, and there is no change in appearance on adding the
mercuric chloride dissolved in the water.
If, however, the mercuric chloride solution is added to
the lime water the yellow oxide of mercury (yellow wash) is
precipitated. On adding the zinc chloride solution and al-
lowing it to stand the precipitate is changed within two hours
from a dense yellow to a flocculent white precipitate.
If the lime water is added to the solution of mercuric
chloride a red-brown precipitate of oxychloride of mercury
is formed, and this is replaced by a white precipitate when the
zinc chloride is added.
That the lime water precipitates nearly all of the mercuric
chloride when these two chemicals are brought together in
the above proportions is evidenced by taking some of the
clear supernatant liquid and passing hydrogen sulphide gas
through it and getting little or no black precipitate of mer-
curic sulphide. If some of the clear solution is taken after
the zinc chloride has been added and the yellow precipitate
turned white, and this solution is treated with hydrogen sul-
phide, a heavy black precipitate of mercuric sulphide is pro-
2o8 INCOMPATIBILITIES IN PRESCRIPTIONS,
duced, showing that the mercuric oxide has been dissolved
and the zinc precipitated. Owing to the fact that the mercury
is in solution, this prescription might be dangerous if applied in
large amounts to an abraded surface, since if all of the mercury
is redissolved it will be in the proportion of about i to 500.
Piperazine is strongly alkaline and when added to an
aqueous solution of phenocoll hydrochloride precipitates the
insoluble base phenocoll. Under certain circumstances, as
when the phenocoll hydrochloride is from fifty to one hun-
dred per cent, in excess of the piperazine, a clear solution is
said to be obtained. This prescription was filled by dissolving
the phenocoll hydrochloride in the elixir, syrup, and pepper-
mint water, and the piperazine in the water. The two solu-
tions were mixed, making a clear solution, which remained
clear for two days. It then happened to be chilled at night
and crystallization took place, making an almost solid mass,
which remained so even at the ordinary temperature. On
warming a solution resulted, which remained clear at the
ordinary temperature, but again solidified on being chilled.
The ammoniated tincture of guaiac if it has not been ex-
posed too long to light and air gives a blue color with the
tincture of iron, but an old tincture of guaiac gives a brown-
black. The tincture of aloes gives a green-brown to a black-
brown with the iron. There is not enough of ammonia in the
ammoniated tmcture of guaiac to form the ferric hydroxide un-
less the tincture of guaiac is freshly made with a fresh aro-
matic spirit of ammonia and the tincture of iron is free from
excess of acid. Even then the syrup will tend to keep the ferric
hydroxide in solution. The syrup precipitates the resinous
matter from both tinctures. The resultmg mixture is nearly
black and very turbid.
INCOMPATIBILITIES IN PRESCRIPTIONS. 209
The dose of the morphine sulphate is considerably in
excess of the amount usually given. The prescriber shows
his knowledge and appreciation of this fact by putting three
exclamation-points after the ingredient. The prescription
should be filled as written. Some physicians when wishing
to give unusual doses underscore the ingredient and the quan-
tity. The latter is perhaps a better method^ as there is less
danger of a mistake. The directions are: Mix. Dispense in
10 capsules. Label: Let one be taken during the night.
On mixing these ingredients a blue-black solution is ob-
tained. This is due to the presence of some ferric sulphate.
Ferrous sulphate as found in drug-stores nearly always con-
tains some ferric sulphate. If strictly ferrous sulphate is used
tannic acid gives no coloration with it.
This prescription was filled by dissolving the clear crystals
of ferrous sulphate in water, adding four grains of sodium
thiosulphate and two drops of sulphuric acid, and boiling
until all of the ferric iron was reduced to the ferrous, as shown
by adding a drop of this solution to a solution of potassium
sulphocyanide and getting no red color. The tannic acid
was dissolved in another portion of water, the syrup added,
and this added to the iron solution. A colorless liquid was
obtained, astringent but not inky in taste. In three days the
solution had assumed a green color and in ten days it was
blue-black. This change, caused by the oxidation of the iron
by the air, would have taken place sooner if the bottle had
been opened frequently.
This prescription can be filled in one of two ways. The
chloral hydrate may be dissolved in the water, and the cam-
phor powdered and mixed with the syrup and then with the
2IO INCOMPATIBILITIES IN PRESCRIPTIONS.
solution of chloral. The camphor will rise to the top. Or
the camphor may be triturated with the chloral hydrate until
liquefied, and this shaken with the syrup and water. The
oily chloral-camphor does not dissolve in the water, but
seems to be decomposed by it, the chloral going into solu-
tion and the camphor coming to the top as a soft white solid.
There seems to be no difference in the final result as to which
method of filling is used. In either case the mixture is a
difficult one to pour so as to get an even dose of the camphor.
A more elegant preparation would be made hy dissolving
the camphor in a little expressed oil of almonds and then
emulsifying it with acacia.
On adding the phosphoric acid to a solution of the
iron and quinine citrate a white precipitate forms which
gives tests for iron but not for quinine. It is prob-
ably iron phosphate and is soluble in a considerable ex-
cess of the acid. When the dilute phosphoric acid is further
diluted with water and then added to the iron salt dissolved
in the balance of the water with the syrup, little or no pre-
cipitation takes place. When the tincture is added to this,
a turbidity results and the mixture acquires a dark green color,
due to the precipitation of matter from the tincture and the
formation of tannate of iron.
In lightly mixing the first two ingredients when powdered
and perfectly dry no change in color is noticed; triturated
together with considerable pressure, the powder turns gray.
As soon as moisture comes in contact with the mixed pow-
ders they become dark g^ay — ^the coloration is due to the
formation of metallic mercury — ^while at the same time a part
of the calomel is changed to mercuric chloride and mercuric
cyanide. (See No. 192.) A translation of the latter part of
the prescription is: Tragacanth, water, of each a quantity sufl&-
INCOMPATIBILITIES IN PRESCRIPTIONS. 211
cient to make a mass which is to be formed into 30 pills. Label:
Take two pills every night.
Soluble metallic salts frequently throw the volatile in-
gredient of medicated or aromatic waters out of solution.
In this case there will be a separation of camphor, which will
rise and float on top. The amount is so small that it may be
disregarded or filtered out.
The Rochelle salt throws some of the camphor out of
solution. Then on the addition of the aromatic sulphuric
acid the tui'bidity is increased on account of the separation
of the oil of cinnamon and the resin of ginger. Chemical
reaction takes place between the Rochelle salt and the sul-
phuric acid, the sodium sulphate going into solution and
potassium bitartrate being precipitated.
Fowler's solution is alkaline in reaction and has a ten-
dency to precipitate the alkaloids from the fluidextract, but
this is prevented by the alcohol in the elixir. The Fowler's
solution contains some carbonate and bicarbonate of potas-
sium, which are said to be incompatible with antipyrine. Am-
monium iodide generally contains a little free iodine, and
iodine coAibines with antipyrine. Practically, however, this
prescription can be filled without difficulty or danger.
Strychnine (free alkaloid) is soluble in 6700 parts of water.
There is enough of water and alcohol in the elixir to prevent
the aromatic spirit of ammonia from throwing it out of solu-
tion. The ammonia will not precipitate the alkaloids of the
212 INCOMPATIBILITIES IN PRESCRIPTIONS.
elixir of cinchona. The above mixture will not be clear, how-
ever, because the oils in the aromatic spirit will te separated
by the elixir. If the spirit of ammonia were used instead of
the aromatic spirit a clear dark-red solution would be ob-
tained. This substitution would not be allowable without
the prescriber's consent.
All of the ingredients except the syrup can be mixed
without producing m\ich turbidity. But on adding the
syrup to this mixture the resinous matter from the fluid-
extract and tincture is precipitated, and the copaiba, oil of
turpentine, and camphor are separated. To make a present-
able mixture some emulsifying agent must be used.
This mixture makes a solid mass and cannot be applied
with a brush. A gelatinous mass which possibly might be ap-
plied with a brush is obtained when one half of the collodion is
replaced by alcohol.
If the Fowler's solution is added to the tincture of nux
vomica the alkali in the solution will liberate the free alkaloid
strychnine, but it will be held in solution by the alcohol until
the infusion is added. With the addition of most infusions
the alkaloids would be precipitated, but the infusion of cin-
chona contains sulphuric acid, which combines with the
alkaloids, forming a soluble salt. The water of the infusion
will precipitate some of the inert matter from the tincture.
When solution of lead subacetate is added to mucilage
of acacia a solid gelatinous mass is formed. In this prescrip-
INCOMPATIBILITIES IN PRESCRIPTIONS, 213
tion if both are diluted with the water and mixed with con-
stant stirring the acacia is precipitated in small masses.
Neutral lead acetate does not gelatinize mucilage of acacia.
The silver nitrate is entirely precipitated by the sodium
chloride as silver chloride. It is customary to filter eye-
washes, and if this one is filtered there will be only a very
weak solution of sodium chloride and sodium nitrate left.
There is no admissible method by which the precipitation can
be prevented without changing the prescription.
If concentrated solutions of the first two ingredients arc
mixed a reddish-brown salicylate of iron is precipitated.
The citric acid in the syrup of lemon precipitates salicylic
acid from a concentrated solution of lithium salicylate. By
dissolving the iron salt in a part of the water and adding the
syrup, then dissolving the salicylate in the balance of the
water and mixing the solutions, a clear deep-red solution can
be obtained. The deep-red color is due to the ferric salicylate
The calcium hypophosphite slowly reduces the mercuric
chloride to mercurous chloride and finally to metallic mer-
cury. This precipitation is not readily seen in the syrup of
sarsaparilla, but if water is used instead of the syrup a tur-
bidity is noticed as soon as solutions of the salts are brought
together. The syrup of sarsaparilla also has a tendency to
reduce the corrosive sublimate, but only very slowly.
The maximum dose of santonin, as given by most authori-
ties, is four grains, some giving as high as five grains. Hav-
214 INCOMPATIBILITIES IN PRESCRIPTIONS.
ing two maximum doses coming so close together renders
this prescription a dangerous one. Prescriptions containing
santonin should be protected from the light, as light causes a
change in color from white to yellow, probably with the
formation of new compounds. Inquiry should be made to
determine whether it is for a child or an adult and if for the
former the prescription should not be filled, as two grains are
said to have killed a child.
This mixture is far from being a solution. The benzoin
and the Tolu are only partially soluble in alcohol and the
acacia is insoluble. The insoluble matter quickly settles to
the bottom of the mixture, forming a layer nearly equal in
depth to that of the supernatant liquid. It, however may
be readily diffused through the liquid by agitation. A
" Shake well " label is necessary.
A clear solution is formed at first, but in about a half
hour needle-shaped crystals begin to fall. The precipitate in-
creases for several hours and contains strychnine which is
thrown out of solution with the iodide. Much commercial
potassium iodide contains a carbonate, but in this case an
iodide free from carbonate was used. It has been suggested
to use acacia to suspend the precipitate, but it is objectionable
if not dangerous to send out a shake mixture in which strychnine
Borax is alkaline in reaction and precipitates nearly all
alkaloids from solutions of their salts. It precipitates the
cocaine in this prescription, but the difficulty can be pre-
INCOMPATIBILITIES IN PRESCRIPTIONS, 215
vented by the use of a little glycerin. The glycerin acts
chemically on the borax, breaking it up and forming sodium
metaborate and boric acid. (See No. 141.) If boric acid
were used instead of borax no precipitation would occur.
The acids were dissolved in the water and then the cocaine
hydrochloride was added, getting a white precipitate at once.
This is the borosalicylate of cocaine. If either add is left out
or if the amounts of both are reduced to one half the amounts^
there will be little or no precipitation.
When the sodium salicylate dissolved in a little water is
added to the quinine sulphate dissolved in the balance of the
water with the aid of the hydrobromic acid, a curdy sticky
precipitate is formed that cannot be mixed with the liquid.
Two chemical reactions take place. Sodium salicylate with
quinine sulphate forms sodium sulphate and the nearly insolu-
ble quinine salicylate. Hydrobromic acid with sodium salicy-
ate forms sodium bromide and the nearly insoluble salicylic
acid. Permission to use alcohol or some other solvent should
On mixing solutions of the first two ingredients a reac-
tion takes place, with the formation of free iodine and a
reddish-brown precipitate. The aqueous solution of iron and
quinine citrate is acid, and ferric salts in acid solutions with
potassium iodide are reduced to ferrous compounds, iodine
being liberated. Iodine in an aqueous solution of potassium
iodide is a general alkaloidal reagent and precipitates the
2l6 INCOMPATIBJUTIES IN PRESCRIPTIONS,
quinine. Neutralizing the solution w^ll prevent liberation of
iodine for a time.
This prescription is frequently given as an example of the
incompatibility of bromides with strychnine salts. It is said
that crystals of strychnine bromide will form after the mix-
ture has been standing for a half hour. The writer failed
rei>eatedly to get a precipitate even on making the solution
twice as strong as that called for and also varying the propor-
tions. The precipitation is partially explained by some
writers by saying that the strychnine bromide is soluble in
water, but insoluble in a solution of potassium bromide. In
many instances the commercial potassium bromide is alka-
line, due to the presence of a carbonate which has been left
in to aid the preservation of the bromide. The carbonate
precipitates the strychnine as the free alkaloid.
Although the Fowler's solution is alkaline, there is enough
of acid in the prescription to prevent any precipitation by it.
The insoluble ferric phosphate or hypophosphite is thrown down.
By using the tincture of citro-chloride of iron no precipitation
results at once, but does after a day or two. If it were admissible
to use twice as much phosphoric acid as tincture of iron there
would be no precipitation.
It is a somewhat disputed question whether in such a
prescription there would be any mercuric chloride formed,
and if so whether the amount formed would be sufficient to
have any disagreeable physiological effect. If the prescrip-
tion is to be used up in a short time probably no bad results
would follow. [See Hydrargyri Chloridum Mite, No. 7.]
INCOMPATIBILITIES IN PRESCRIPTIONS. 217
Terpin hydrate dissolves in about 250 parts of water and
iodol in about 5000 parts of water. These should be finely
powdered before mixing with the other ingredients, and the
prescription dispensed with a " Shake well " label. The
glycerin and syrup are sufficiently viscid to keep the insoluble
substances in suspension for a time.
Each ingredient should be powdered separately and then
mixed lightly with the other. If the two are rubbed together
with some force slight crackling explosions take place. A
sharp blow would probably cause serious results. The patient
should be cautioned. With a little care on the part of the
pharmacist and patient no ill results will follow from this
In this mixture the menthol floats on top and the boric
acid goes to the bottom. Using alcohol, glycerin, or a fixed
oil instead of water will not make a clear solution. The at-
tention of the physician should be called to this prescrip-
Santonin is soluble in about 40 parts of alcohol, nearly
insoluble in water, and not readily soluble in turpentine. The
amount prescribed is not all soluble in the mixture. The
turpentine does not mix, but floats on top. Extractive mat-
ter from the fluid extracts is precipitated. The santonin
should be in the form of a fine powder and the mixture made
into an emulsion.
2l8 INCOMPATIBILITIES IN PRESCRIPTIONS.
The potassium carbonate is deliquescent. It should be
powdered with some absorbent powder, such as althaea, and
then the arsenic, previously triturated with some sugar of
milk, added. Next add the mass of iron and if necessary a
little water. The pills should be dispensed in a bottle pro-
tected from the atmosphere; otherwise they will become soft.
This solution has a much larger proportion of active in-
grredients than is usually prescribed in an eye-wash. Probably
the prescriber meant grains instead of drams. It should not
be dispensed without consulting the physician, as it would
cause intense irritation. In case the prescriber cannot be reached
and it seems urgent that the prescription should be filled the
quantities can be reduced to grains and the prescriber notified
at the earliest opportunity.
Mixing a solution of silver nitrate with a solution of
cocaine hydrochloride produces a white precipitate of silver
chloride. If this is filtered out about one half of the silver is
removed. The pharmacist should use cocaine nitrate. If he
does not have it he can make it by dissolving the one grain
of cocaine hydrochloride in a little water and adding one half
a grain of silver nitrate in a little water. This makes cocaine
nitrate and silver chloride. The precipitate can then be fil-
tered out and the requisite amount of silver nitrate added.
Borax is soluble in i6 parts of water, and in this case
there is not enough to dissolve it Boric acid requires i8
INCOMPATIBILITIES IN PRESCRIPTIONS. 219
parts of water to dissolve it, but it is much more soluble in a
solution of borax. The principal difficulty with this prescrip-
tion is that the mucilage of acacia is gelatinized by the borax,
making a stiff mass. Boric acid has not the effect of gelati-
nizing acacia, and borax is prevented from doing so by the
presence of sugar. Glycerin also prevents this action by de-
composing the ttorax.
The first two ingredients are both disinfectants and oxi-
dizing agents, yet they react on each other, with the reduction
of both. The chemical reaction is represented by the follow-
2KMn04 + 5H2O2 + 3H2SO4
= 5O2 + 8H2O + K2SO4 + 2MnS04.
The acid necessary for the reaction is usually present in the
hydrogen dioxide water, as a small amount is allowed to remain
for preservation of the dioxide. The amoimt of hydrogen dioxide
which 20 grains of potassium permanganate would act upon is
10.7 grains. If the dioxide water is official i fluid ounce con-
tains about 13.7 grains of hydrogen dioxide, which would be
sufficient to reduce all of the permanganate. Usually there
will be a precipitate of manganese dioxide, there not being enough
of acid to convert all into a salt. By adding a grain or two of
sodium bicarbonate to neutralize the acid some of the change
can be prevented. The directions are: Let them be mixed by
vigorous shaking. Label: Let it be applied to the affected parts