SCIENTIFIC SUMMARY. 
425 
Mica a Substitute for Bronze. — The practical value of mica may by this 
means be much increased, but we doubt the possibility of making it a real 
substitute for bronze. The following quotation is taken by the Chemical 
News from the Journal fur prakt. Chemie. The mica is reduced to small 
pieces in a stamping mill, digested with chlorhydric acid, cleansed by wash- 
ing and sorted by sieves into sizes. The mica scales so prepared have a 
beautiful vitreous lustre, a silvery appearance, and bear in commerce the 
name of brocade crystal colours or mica bronzes. The advantages of these 
brocades over the common metallic ones are — 1. They contain no unwhole- 
some substance. 2. They possess a metallic lustre like the metallic bro- 
cades, and much surpass them in splendour. 8. Brown, blue, black, green, 
and red colours of rare brilliancy can be obtained, which is not the case with 
the metallic brocades. 4. They are not dimmed by sulphur vapours. The 
analyses by Drs. Cech and Schneider show that the colouring matter of the 
rose-brocade is cochineal ; that of carmine is fuchsine ; bright red, fuchsine, 
and Havanna brown ; violet, Hofmann’s violet ; bright blue, Berlin blue ; 
dark blue, probably impure aniline blue or Girard’s violet ; light and dark 
green, a mixture of aniline blue and curcuma ; gold, curcuma ; silver, the 
mica alone, &c. 
How to Estimate Glacial Acetic Acid Quantitatively. — The Chemical News f 
quoting from a German journal, says, that F. Biidorff* preliminarily refers to 
the usual methods of the estimation in question, by means of a titrated soda 
solution, stating it to be unsatisfactory ; and next mentions that his method 
is based upon the estimation of the freezing-point of the acid in question. 
The author enters at length into the details of his experiments, the chief 
point of interest of which is that perfectly pure and anhydrous acetic acid 
solidifies at 16° # 7 ; that if either water, alcohol, some salts, or sulphuric acid 
are present, these substances tend to lower the point of solidification, so that 
100 parts of the pure acid, mixed with 24 of water, solidifies at -7° *4. 
Amorphous Silica for Fixing Eyes. — In Dingier 's Polytechnischcs Journal 
(second number for June) Dr. M. Reimann describes a series of experiments 
made with the view to apply amorphous silica (as obtained by precipitating 
a solution of so-called water-glass, silicate of soda, or potassa, with an acid, 
and collecting, washing, and drying the precipitate in the ordinary way) for 
absorbing the solutions of fuchsine, aniline blue, &c., and to apply the 
coloured powder so prepared as a pigment for various materials. The 
author states that glass, first superficially acted upon by hydrofluoric acid, 
and next mordanted, as is usual for cotton, assumes, when submitted to the 
processes in use for dyeing fibre, precisely similar colours as that fibre, and 
that this effect is caused by the amorphous silica contained in the glass and 
made active by the hydrofluoric acid. 
A Test for Water in Milk. — It is, as is well known, a remarkably difficult 
matter to detect water in milk, so as to say for certain that it has been 
added. A test which appears likely has been devised by Dr. A. E. Davies, 
F.C.S. Such a test, he believes, we have in the specific gravity of the serum, 
or liquid portion of the milk, from which the caseine and fat have been re- 
moved by coagulating and straining. The gravity of this liquid he has 
found to be remarkably constant, ranging, in that obtained from genuine 
milk, from 102G to 1028 ; and, by carefully ascertaining the specific gravity 
