1816.} . Royal Society. 305 
and opium immediate drowsiness. We know at present only two 
specific medicines; namely, mercury for the venereal disease, and 
the eau medicinale, which is a vinous infusion of colchicum autum- 
nale, for the gout. It is well known that mercury produces its 
effects only when introduced into the circulation. The author 
gives an account of several experiments with the eau medicinale on 
himself and on dogs, which shows that it requires likewise to be in- 
troduced into the circulation before it produces its effects. 
At the samé meeting part of a paper by Dr. Thomson, on the 
composition of phosphoric acid, was read. Lavoisier first ascer- 
tained that this acid is a compound of phosphorus and oxygen. 
The result of his numerous experiments was, that this acid is a 
compound of two parts of phosphorus by weight, and three parts 
of oxygen; but there is reason for believing that he over-rated the 
proportion of oxygen, owing to circumstances mentioned in the 
paper. Rose made a set of experiments at a much later period, 
partly in the same way as Lavoisier had done, and partly by acidi- 
fying phosphorus by means of nitric acid. According to him, 
phosphoric acid is a compound of 100 phosphorus + 114°75 oxy- 
gen; but when his numbers are corrected by a more accurate ana- 
lysis of phosphate of lead than he possessed, they are reduced to 
100 phosphorus, and rather less than 100 oxygen: so that the pro- 
portion of oxygen which he found in the acid was too small. 
On Thursday the 28th of March Dr. Thomson’s paper was 
finished. The author made many experiments to determine the 
constituents of phosphoric acid, by acidifying phosphorus by means 
of nitric acid; but the results were unsatisfactory. He therefore 
had recourse to the method of Lavoisier, Small quantities of 
phosphorus (as one grain or 3 of a grain) may be burnt in glass 
retorts by the heat of a lamp, without leaving any sensible residue. 
The mean of a variety of experiments made by the author in this 
way is that a grain of phosphorus, when converted into phosphoric 
acid by combustion, absorbs three cubic inches and two thirds of 
oxygen gas. From this result it follows that the acid is composed 
of 
Oxygen ...... Smoot OS ic ear 12346 
Acid, Base, 
By Wollaston “fe ee eeeee ee 100 + 370°72 
Berzelius..: ........5. 100 + 380°56 
Thomson ......6...0.«. L0@ + 39849 
PT ea, eet rao 100 + 3383°26 
