176 Scientific Intelligence. 
the pyrolignite spirit comes. over first; then follows the acetic acid, 
with water and empyreumatic oil, colorless, and there remains in 
the retort a dark brown mass, similar to extract.—/Ann. des Mines, 
Tom. V. p. 78 
16. New method of discovering the presence of Nitric Acid, by 
Just. Leibig. (Ann. de Chem. t. 35, p. 80.)—Mix the liquid to 
be examined with as much indigo as is necessary to color it distinct- 
ly blue ; add a few drops of concentrated sulphuric acid, and heat it 
to ebullition. If the liquid contains a nitrate it is discolored, or if 
the portion of nitrate is very small, its blue color changes to yellow. 
In adding to the liquid a little muriate of soda, prior to heating it, 
we may easily detect the presence of =}, of nitric acid.—Jdem., 
17. Reduction of Boracic Acid by Hydrogen ; by M. Varvinsh. 
(Fer. Bull. Tom. 10, p. 159.)—When hydrogen gas is passed 
through a porcelain tube filled with boracic acid in scales, and heated 
to redness, the acid is vitrified, and colored brown. If after this ope- 
ration, it is treated with boiling water, there remains a floculent and 
olive colored substance, which is no other than boron.—Jdem. 
18. On Pyrophorus ; by Gay Lussac—(Ann. de Ch. t. 37. 
p- 415.)—The causes to which pyrophorus owes its inflammation 
not appearing to me sufficiently determined, I made the following 
experiments : 
A mixture of calcined alum and calcined lampblack was heated in 
an earthen retort. Carbonic acid and sulphurous gases are at first 
_ disengaged, in nearly equal volumes ; then carbonic acid, pure, but 
afterwards mixed with oxide of carbon, which in the end became 
predominant. ‘The remainder, when quite cold, inflamed like the 
best pyrophorus, spreading a suffocating odour, of sulphurous acid, 
and burning even with a slight blue flame. This pyrophorous is @ 
mixture of carbon, alumine, and poly-sulphuret of potassium, which 
is formed at the expense of a part of the sulphuric acid, and sulphate 
of alumine. 
The carbon is not indispensible to its formation ; for, by employ- 
ing 1 gr. alum, and 3.33 gr. of calcined lampblack, I obtained a 
teddish matter, in which there remained no carbon, and which 
was very inflammable. | 
