A NEW SALT OF COPPER. 
331 
water, even small as it is, by contact with the atmosphere. 
But it is only sufficient to submit it to compression, to find 
that the aggregate of minute crystals are impregnated with 
water; and if this be done between sheets of blotting paper, 
they will be thoroughly moistened. 
The quantity of water which abandons the blue salt in its 
transformation to the green one, is from 26 to 48 per cent.; it 
is four times as much as what still remains in the latter, that 
is to say, in the ordinary crystallized verdigris. The blue 
salt then contains 33.11 per cent, or 5 atoms of water; it is 
obtained in a very simple manner by dissolving verdigris in 
water acidulated by acetic acid, at a temperature below the 
point of ebullition and then allowing it to crystallize. 
Jour, de Phar. from the Ann. de Physik und Chemie. 
ART. LVI.—ON THE PRESENCE OF ARSENIC IN PHOS- 
PHORUS. 
Mr. Hertz an apothecary having observed that phosphoric 
acid prepared according to the Prussian pharmacopoeia, by 
treating phosphorus with nitric acid, becomes of a yellow co- 
lour on the addition of a solution of sulphuretted hydrogen, 
Mr. Barwald made some experiments on the subject; he passed 
a current of sulphuretted hydrogen through phosphoric acid 
prepared in the same way, and obtained from a pound of the 
acid, eight grains of a yellow precipitate, which when mixed 
with carbonate of soda, was decomposed in a glass tube, by 
means of dry hydrogen. 
A metallic ring was formed at the upper part of the tube, 
which, from its appearance and its odour when placed on live 
coals, was ascertained to be metallic arsenic. Phosphoric acid 
from other shops in Berlin, afforded the same results. Mr. 
Barwald satisfied himself by careful experiments that neither 
the vessels employed, the nitric acid used in preparing the 
