138 
SELECTED ARTICLES. 
trie acid attacks it strongly, and changes it at first into a yel- 
low, azotated body, nitrosalicide, and afterwards into an acid 
which possesses the principal properties of carbazotic acid. 
The two products will be described separately. 
The most advantageous method to obtain the hyduret of sa- 
licyle is the following: — Dissolve, in a suitable quantity of 
water, four parts of bichromate of potassa, and add to it 
three parts of concentrated sulphuric acid. On the other hand, 
prepare a tubulated retort, connected with a receiver, surround- 
ed with cold water; introduce into the retort the quantity of 
salicin, on which the operation is to be performed, along with 
six times its weight of water, and apply heat. When the sali- 
cin is dissolved, and the solution has attained the boiling point, 
pour in through the tubulure, by small quantities at a time, the 
solution of bichromate of potassa and sulphuric acid. At each 
addition, a quick reaction will be manifest; the mixture as- 
sumes a green color, from the formation of sulphate of chromi- 
um, in a short time a milky water distils over, holding the 
hyduret of salicyle in suspension. By rest, the hyduret is de- 
posited at the bottom of the receiver, from whence it may be 
withdrawn by means of a pipette. 
Before entering into the details relative to the composition 
of the hyduret of salicyle and the compounds derived there- 
from, I will dwell for a moment on the circumstances which 
accompany its production. 
We cannot but be struck with the singular difference which 
is to be remarked between the products which salicin furnishes, 
under the influence of different oxidating bodies. As I 
have already said, when treated with sulphuric acid and perox- 
ide of maganese, it yields only carbonic and formic acids. It 
is the same with a mixture of peroxide of lead and sulphuric 
acid; but when bichromate of potassa is substituted for the me- 
tallic peroxides, the products of the reaction are very different. 
An attentive examination of the conditions under which the 
salicin is placed in these cases, naturally leads to the question, 
whether the presence or absence of a free acid could modify 
the nature of the resulting products. When we treat the sa- 
