D. CHEMISTRY AND METALLURGY. 213 



tannin will absorb 20 cubic centimeters of oxygen. A grad- 

 uated glass tube, with a glass stop-cock at the bottom and a 

 ground-glass stopper at the top, is partially filled with 333- 

 per cent, solution of potash, and the substance in which the 

 tannin is to be determined is introduced as finely pulverized 

 as possible and wrapped in unsized paper, and the tube then 

 closed, the temperature and barometric pressure being noted 

 at the same time. The liquid immediately begins to turn 

 brown, and after twenty-four hours the amount of oxygen is 

 read off, by opening the stop-cock under water, and from it 

 the quantity of tannin present is calculated. 32 C, May 16, 

 1874, 239. 



COMPOSITION OF SUINT. 



Besides free cholesterine present in suint, Schulze has also 

 detected in it a compound ether, containing cholesterine and 

 isomeric with it, which he has named isocholesterine. It 

 crystallizes out of ether and acetone in fine transparent 

 needles, and out of alcohol in gelatinous masses ; melts at 

 278 to 280, and volatilizes at a high temperature, without 

 decomposition. 13 C,3Tay, 1874, 604. 



SAFE HYDROGEN GENERATORS. 



Dr. Fresenius, with a view to avoid the dangers of explo- 

 sions in hydrogen generators, which, as every chemist knows, 

 are of frequent occurrence despite the exercise of both pa- 

 tience and care, has applied thereto the principle of the Davy 

 safety-lamp. A number of discs of fine Avire gauze are 

 placed in a short glass tube, and held in position by cotton- 

 wool pressed against them on both sides. This little tube is 

 introduced near the exit of the gas, and prevents the explo- 

 sion from extending to the wash bottle, and the generator 

 itself. 



NEW PROCESS FOR ESTIMATION OF ALCOHOL. 



The latest novelty of this sort is the process devised by 

 M. Ducleaux, which is described as follows : If to a known 

 volume of water larger and larger quantities of alcohol are 

 added, the density and superficial tension of the mixtures 

 obtained are simultaneously diminished, and there is conse- 

 quently an increase in the number of drops which they form 



