218 
ACIDS AS TESTS FOR AltSENIC. 
We confess we entered upon tlie consideration of this 
subject with a degree of hesitation, amounting to reluct¬ 
ance ; not from any apprehension that our views were incor¬ 
rect, but lest, being misunderstood, we should give offence 
to some. Fortunately most do not come under this denomi¬ 
nation. Our observations are, therefore, only of very 
partial application. There are those among us who per¬ 
form the arduous duties of their profession in a true love 
of it. Diligence and self-sacrifice mark their course. They 
are also esteemed by their employers for their scientific 
acquirements. They obtain the guerdon, and we are proud 
of them, for they enhance the usefulness and importance 
of our art, while they promote its progress and increase its 
estimation by the discerning and the wise. 
Extracts from British and Foreign Journals. 
DIFFICULTY IN OBTAINING THE ACIDS PURE THAT ARE 
USED IN MARSH’S AND RIENSCH’S TESTS FOR ARSENIC. 
In a paper read by Mr. Bloxam, at a late meeting of the 
Chemical Society, a On Arsenic in Sulphuric Acid/* he 
stated that he had found that no samples of hydrochloric or 
sulphuric acid were free from this impurity. The quantity 
was sometimes very small, but still it would be satisfactory 
in medico-legal inquiries to possess an acid containing no 
traces of the metal. Various methods for the purification of 
sulphuric acid had been tried—for instance, distillation with 
chloride of sodium, both concentrated and dilute acid being 
employed; also, passing hydrochloric acid gas through a 
boiling solution of sulphuric acid, electrolysing, fractional 
distillation, distillation with oxydising agents. None of these 
processes, however, were successful. He next tried oxydising 
sulphurous acid by passing it over pumice-stone which had 
been coated with platinum black, but the pumice-stone itself 
yielded up arsenic. Nitric oxide was next employed as an 
oxydising agent, the sulphurous acid being prepared from sul¬ 
phuric acid and copper. Mercury was employed in some of 
the experiments for the preparation of the sulphurous acid, 
on account of the arsenic present in copper. As a last 
resource, crystallized sulphite of soda was employed as a 
