Intelligence and Miscellaneous Articles. 93 



NEW ALUM. BY DR. MOHR. 

 A variety of alum has been for some time introduced into Ger- 

 many, which is recommended as containing the principles necessary 

 to dyeing and calico printing in a state of great concentration ; this 

 quality is represented as rendering its use more advantageous, and 

 less expensive in carriage. This alum has not the slightest resem- 

 blance to common potash alum ; it exists in flat quadrangular tables, 

 which are slightly transparent, and dissolve very readily in water ; 

 the taste of this salt is sweetish, acid, and aluminous, and much 

 more distinctly so than common alum ; when heated in a crucible 

 it swells, and eventually becomes a gummy mass, which, when more 

 strongly heated, gives out sulphuric vapours. Nevertheless the mass 

 which has been heated to redness is entirely and readily soluble in 

 water. If pulverized sulphate of potash be thrown into a concen- 

 trated solution of this alum, a crust of common alum is quickly 

 formed. The usual reagents prove that it contains sulphuric 

 acid, alumina, and a small quantity of potash, but no ammonia. 

 M. Mohr found it to consist of 



- Sulphuric acid 36*24 



Alumina 1391 



Potash 1-50 



Water 49-60 10M5 



This composition shows that the alum in question is, properly 

 speaking, merely sulphate of alumina with an excess of acid, and 

 combined with water of crystallization. The small quantity of sul- 

 phate of potash shows the origin of this salt, it being probably pre- 

 pared with pulverized and calcined pipe-clay and sulphuric acid not 

 completely concentrated. This new alum is entirely free from iron. 

 — Journal de Pharmacie, t. xxvi. p. 633. 



ON THE SUPPOSED HYDRATE OF PHOSPHORUS. BY M. MAR- 



CHAND. 



M. Pelouze was the first chemist who supposed that the white 

 crust which covers phosphorus that has been long kept, is a hydrate 

 of this substance : M. H. Rose regards it merely as a modification 

 of the state of aggregation : M. Mulder believes that it is a com- 

 pound of oxide of phosphorus and phosphuretted hydrogen. He has 

 remarked that the white sticks of phosphorus become of a red co- 

 lour in aerated distilled water, and he immediately obtained a si- 

 milar white substance by subjecting red oxide of phosphorus to the 

 action of phosphuretted hydrogen. 



M. Marchand being desirous of settling the question, pressed a 

 quantity of the white crust, strongly, between folds of filtering 

 paper, as had been done by M. Rose ; he then placed it in a capsule 

 over sulphuric acid in vacuo, and allowed it to remain so for several 

 days. On the first day a feeble light was perceptible ; but it soon 

 disappeared : and when access of air was allowed the mass inflamed 

 as if it had been phosphorus under similar circumstances. 



A fresh quantity of the white crust was again dried over sulphuric 

 acid, but under a receiver without a vacuum. M. Marchand placed 



