PHOSPHATE OF LIME IN SUBNITRATE OF BISMUTH. 
347 
the amount of solid matter in a weighed quantity of the liquid; and, in addi¬ 
tion, take its specific gravity. That remained to be done for fully one-half of 
the tinctures that were now given in the Pharmacopoeia, so that there was no 
lack of work for those who chose to take up this subject. 
Mr. Burden remarked that Dr. Redwood had not told them what was the 
condition of the ingredients when they were put into the apparatus he had de¬ 
scribed, and he should like to know whether the cylinder was thrust in whilst 
the bag was full of ingredients. He should be glad to hear what practical men 
who had to sell these things had to say with reference to Dr. Redwood’s appa¬ 
ratus. From the little experience he had had, he was of opinion that percolation 
was certainly the most perfect process for the generality of tinctures in the 
Pharmacopoeia ; but it required a great deal of care, and much time was occu¬ 
pied in preparing and manipulating the ingredients. It appeared to him that 
the standing for forty-eight hours, ordered in theB. P., was in order that certain 
extractive matter should be dissolved and softened, and it was necessary they' 
should know how long it took to soften the extractive matter in the ingredients. 
Mr. Haselden spoke very truly of the necessity to pass the remaining 25 per 
cent, through the ingredients ; but he had found that, in many instances, there 
was no necessity to pass through 25 per cent, of the spirit*at all, that the ex¬ 
tractive matter was all got out. With regard to tincture of opium, he had pre¬ 
pared that by percolation, and it was one of the most troublesome tinctures they 
had to deal with. A large amount of extractive matter, especially if the opium 
was good, soon stopped the way, so that the spirit would not pass through. In 
that case, he had tried a large quantity of sand, and by gradually putting a 
certain portion, about an inch in depth, and so adding inch by inch he had 
gradually been enabled to get the spirit to pass through in the course of forty- 
eight hours. If they put all into the percolator at once, they would not get it 
through if the opium were good. The difference in the contraction of the spirit 
also made a difference in the loss, the quantity of which was generally from 15 
to 20 ounces per gallon. 
The Chairman thought the Pharmacopoeia process would be improved, if 
instead of taking 75 per cent, of the spirit for maceration, they took 25 per cent., 
and then passed the other 75 per cent, through. That would give more perfect 
percolation and displacement. 
Dr. Redwood thought the proposed alterations would only complicate with¬ 
out improving what the Pharmacopoeia indicates in reference to quantities of 
spirit. The Pharmacopoeia indicated the conditions in which the solid ingre¬ 
dients were to be used. -t, 
ON THE DETECTION OF PHOSPHATE OF LIME IN 
SUBNITRATE OF BISMUTH. 
BY MR. G. G. HORNSBY. 
I was not in time for the September issue of the Journal, or I should have 
sent some remarks on the “Note on a New Adulteration of Subnitrate of Bis¬ 
muth,’’ by Dr. Redwood. I am glad, however, to find that Messrs. Howard 
and Sons have pointed out (what I had previously proved by careful experiment) 
that this test, suggested by Mr. Roussin and supplemented by Dr. Redwood, for 
the detection of phosphate of lime, was fallacious. This point established, I 
have somewhat to say upon the modification suggested by Messrs. Howard and 
Son. 
The process they suggest possesses some advantages over that of Mr. Roussin, 
but cannot, per se , be relied upon, as the following results will show. I have 
operated upon several samples as follows :— 
2 B 2 
