M. Otto on Crystallized Oxide of Chromium. 223 



thallium solution is reduced by a simple voltaic element. For 

 this purpose a short wide glass tube is covered at the bottom 

 with a bladder, and, being filled with acidulated water, is 

 immersed in the thallium solution, so that both liquids are on 

 the same level. A zinc plate is immersed in the acidulated 

 solution, and it is provided with a platinum or copper wire 

 which is bent so that it dips outside in the solution of 

 thallium. The reduction begins at once, and the wire is 

 gradually covered with a beautiful crystallization of thallium, 

 of which in a few days no traces are to be found in the 

 solution. These crystals are washed, pressed, rapidly dried and 

 fused to a regulus in a porcelain crucible with cyanide of 

 potassium. 



According to Otto*, crystallized oxide of chromium may be 

 prepared with ease and in any quantity by the action of hydrogen 

 upon bichromate of potassium at a high temperature, whereby 

 the salt is decomposed into neutral chromate of potassium, water, 

 and chromic oxide, according to the following equation : — 



2Gr 2 K 2 7 + 6H = 2GrK 2 4 + 3H 2 OH-€r 2 3 . 



The dried and powdered salt is introduced into a tube of hard 

 glass, which is gently heated in a suitable furnace, and a current 

 of dry hydrogen is passed through j aqueous vapours soon make 

 their appearance, and within a short time the reduction is com- 

 plete. On cooling, the tube is broken and the dark-green slag- 

 placed in water, which dissolves the neutral chromate, leaving 

 the oxide in the form of small green lustrous flitters. 



SchifFf, itt an investigation on the influence of various liquids 

 on the division of phosphorus, has arrived at the following re- 

 sults : — 



In many cases, but not always, the action of liquids in pulve- 

 rizing phosphorus depends on their density. 



The nature of the liquid has an influence even when its den- 

 sity is less than that of water. 



Viscosity exerts great influence even with solutions of small 

 density. 



Liquids in which there is a slight disengagement of gas are 

 especially adapted for pulverizing phosphorus. 



Deville and Caron artificially reproduced apatite and Wag- 

 nerite, which they regarded as types of two groups having re- 



* Liebig's Annalen, April 1867. 



t Liebig's AnnaUn (Suppl.), vol. iv. part 1. 



