350 Intelligence and Miscellaneous Articles. 



DECOMPOSITION OF BROMATE OF POTASH BY HEAT. 



According to M. Fritzsche, when bromate of potash is sulijected to 

 a high temperature in a mercury-bath, the crystals of the salt de- 

 crepitate, and are reduced to powder. If this powder be thrown into 

 water it immediately disengages pure oxygen gas : the evolution is 

 most rapid when the temperature of the water is raised from about 

 IGO"* to 175°. In the opinion of the author, the bromate influenced 

 by heat is decomposed into bromite and oxibromate, the latter being 

 immediately decomposed by the water into bromate and oxygen gas. 

 It appears that the bromite possesses the property of readily absorb- 

 ing oxygen, and reproducing bromate, for the author found that the 

 powder, dissolved in water and evaporated in the air, reproduced 

 exactly the quantity of bromate originally submitted to experiment. 



The production of oxibromate, under these circumstances, is a 

 curious fact, which connects the bromate with the chlorate of potash ; 

 and the decomposition which the oxibromate undergoes in water, 

 explains how it happens that it has been found impossible to obtain 

 oxibromate of potash in the moist way. — Journal de Pharm. et de 



Chitn., Jan. 1842. 



ON THE LIGHT WHICH APPEARS DURING CRYSTALLIZATION. 

 BY M. H. ROSE. 



By fusing a mixture of one equivalent each of sulphate of potash 

 and soda in a platina crucible, the author obtained a vitreous mass 

 devoid of crystalline texture ; this was dissolved in boiling water and 

 the solution quickly filtered, and allowed to cool slowly in the dark ; 

 it exhibited the same appearance of light as was observed by M . 

 Rose in 183G during the crystallization of a solution of vitreous ar- 

 senious acid in hydrochloric acid ; the formation of each rudiment of 

 a crystal was announced by a spark. Tlie crystals thus obtained ex- 

 hibit nothing similar when re-dissolved ; but if crystals which have 

 been formed with the disengagement of light be taken from the so- 

 lution, they become again phosphorescent when strongly rubbed or 

 pressed ; they do not retain this property for more than a few hours, 

 and have the usual crystalline form of the salt. 



No phosphorescence occurs during the crystallization of the sul- 

 phate of potash, when the vitreous mass is dissolved more than 24 

 hours after its fusion; it appears then to have passed to the crj"^- 

 stalline state. The crystals deposited with phosphorescence are not 

 formed of pure sulphate of potash ; they are a true double salt, which 

 possesses the same crystalline form as sulphate of potash and most of 

 its physical properties. M. Rose found in several experiments a dou- 

 ble salt formed of 2 atoms of sulphate of potash and 1 atom of sulphate 

 of soda ; in other cases, on the contrary, the proportions were 3 atoms 

 of sulphate of potash and 2 atoms of sulphate of soda. 



The phsenomenon of phosphorescence, in the case, of the double 

 sulphate of potash and soda, appears to depend on its vitreous state, 

 which it retains in solution, and passes to the crystalline state at the 

 moment only of its separation from solution. 



M. Rose has found, by a great number of analyses, that the sul- 

 phate of potash of commerce contains sulphate of soda, forming with 



