COCHINEAL COLOURING. 
with solution of nitrate of silver. Having ascertained that the quantity of chlo¬ 
rine required to form Fe 2 Cl 3 with the iron present in the two drachms was 40d 
grains, I found that I should obtain 120^ grains of chloride of silver. I obtained 
exactly 121 grains. This proves, not that there was no basic perchloride pre¬ 
sent in the liquor, but that the condition under which it is formed, namely, de¬ 
ficiency of hydrochloric acid, did not exist. 
I have been led to adopt the following formula as the result of numerous ex¬ 
periments and observations on this subject:— 
Take of Iron, two ounces. 
Hydrochloric Acid, eleven fluid ounces. 
Nitric Acid, sp. gr. 1*5, five fluid ounces. 
Water, seven fluid ounces. 
Dilute seven ounces of the hydrochloric acid with five ounces of the water ; add 
the iron to the mixture, and place it aside in a warm place for twenty-four 
hours, or until the iron is dissolved; filter, then add first the remaining three 
ounces of hydrochloric acid, and then the nitric acid diluted with the remaining 
two ounces of the water; heat briskly until, on the sudden evolution of red 
fumes, the liquid assumes a dark orange-brown colour; then, with a gentler 
heat, evaporate until the liquid is reduced to ten fluid ounces. The above for¬ 
mula contains more hydrochloric acid and less nitric acid than are ordered in the 
Pharmacopceia. Mr. Squire recommends twelve ounces of hydrochloric acid, 
but I think eleven ounces sufficient, especially if the iron be added to the quan¬ 
tity of acid merely requisite for its solution. The five drachms of nitric acid I 
consider sufficient to convert all the proto- into perchloride, and there is less 
likely to be free nitric acid in the solution. 
COCHINEAL COLOURING. 
TO TIIE EDITOR OF THE PHARMACEUTICAL JOURNAL. 
Sir,—Seeing in your February number a new form for cochineal colouring, I 
tried it, with the following results :—After adding the Liq. Ammon. Fort, to 
the infusion, I put a few drops of the colouring in 5 iv of water, and let it 
stand for three hours exposed to the action of the atmosphere, when I found 
that the ammonia had quite evaporated, leaving the liquid of a dirty brown 
colour. Now I conclude from this fact that if this colouring were used in a 
jelly, the ammonia would be evaporated with equal facility, and thus render it 
of such a nasty colour as to be unfit to place on the table. I also found that 
when used as red ink it turned to brown in a few minutes. Again, I put 5j of 
the colouring in £ij of water, and then added gr. y. of citric acid, when the so¬ 
lution turned to an orange colour. Now I believe that lemon juice is sometimes 
taken with jellies. If any were taken with a jelly coloured by this colouring, 
the effect would be that the jelly would be turned from a bright red (if it had 
not already turned brown by evaporation) to a pale yellow, to the great asto¬ 
nishment of the person about to swallow it. Again, I found that this colouring 
became in a few days a ropy and jelly-like mass, and with some difficulty mis¬ 
cible with water. 
Your article entirely, but unjustly, condemned the old form of making the 
colouring with potash, alum, and cream of tartar, but I have proved that this 
form is the best, with a very slight modification. I always found that the old 
colouring became decomposed in about a week in warm weather, and smelt very 
offensive. I tried a small quantity of nitrate of potash to see if that would 
keep it, but found it as bad as ever. I then • tried chloride of sodium (common 
salt) with perfect success, and since then I have kept some for two or three 
