236 Scientific Intelligence. (Marcu, 
V. On Nitrate of Silver as a Test of Arsenic. 
An ingenious student at Guy’s Hospital suggested to Dr. Marcet. 
that when nitrate of silver is mixed with a solution containing an 
alkaline phosphate, a yellow precipitate is thrown down, similar in 
appearance to arseniate of silver. Hence an ambiguity in the mode 
of detecting arsenic in the liquid contained in the stomach, where 
an alkaline phosphate may very well be present. This fact induced 
Dr. Marcet to examine the subject anew. The shade of the two 
salts is not quite the same. Yet in juridical cases other tests may 
be requisite to be assured of the presence of arsenic. The addition 
of sulphate of copper and potash, and the formation of Scheele’s 
green, affords a very satisfactory confirmation. But the best mode 
of proceeding is to mix the supposed arsenite of silver with a little 
potash and charcoal powder, and expose it to heat in a glass tube. 
A pellicle of metallic arsenic will be obtained on the inside of the 
tube, unless the quantity of arsenic present be very minute indeed. 
VI. Query respecting the Use of the Liver. 
(To Dr. Thomson.) 
SIR, 
In the valuable and much admired sketch of the improvements 
in physical science, with which you presented your readers this 
month, I met with the following paragraph, which contains an 
inference the accuracy of which does not immediately appear. This 
is the passage :-— 
s¢ From the discovery of Mr. Rose that urine in hepatitis contains 
no urea, I think it may be inferred that one use of the liver, if not 
the only one, is to separate urea from the blood ; so that it would 
seem to be the principal organ concerned in the formation of urine.” 
1 doubt not but the conclusion appears perfectly satisfactory to 
your own mind, and would probably appear equally so to the minds 
of your readers, if you would be rather more explicit in the state- 
ment of the grounds from which this very important deduction is 
‘drawn. Will you excuse my liberty in requesting you to satisfy me 
and others of your readers by adverting to this subject in the next 
number of your Annals of Philosophy. 
' Edinburgh, Jan, 11, 1816. Dros. 
In hepatitis the liver is diseased ; therefore I infer that it is inca- 
pable of performing its usual function. The disappearing of urea 
being a constant concomitant, I infer that the function of the liver 
in its sound state is to secrete urea. 
VII. Queries respecting Ginger and Gas Light. 
(To Dr. Thomson.) 
SIR, 
It is a fact no doubt known to many of your readers, ‘that when — 
a small quantity of powdered ginger is stirred into ale or beer 
