Improvements in Science. 289 



Article VI. 

 Notice of some Recent Improvements in Science. 



HEAT AND LIGHT. 



Extrication of light in the formation of crystals. — Rose 

 took from two to three drachms of glassy arsenious acid 

 and digested it in a colourless glass vessel, with 1 \ ounces 

 of not fuming muriatic acid of|the usual strength, and half 

 an ounce of water ; he brought the mixture to the point of 

 ebullition, and allowed it to remain at this temperature for 

 10 or 15 minutes, and then cooled it as slowly as possible, 

 by gradually withdrawing the spirit lamp which had been 

 employed in the boiling. When the crystals began to form 

 in a dark place, it was attended with a strong light ; the 

 production of every small crystal being accompanied with a 

 spark. If the vessel be shaken, numerous crystals suddenly 

 shoot out, and a corresponding number of sparks is observed. 

 When the quantity of arsenious acid amounts to an ounce 

 or an ounce and a half, with the quantity of muriatic acid 

 already mentioned, on being shaken, the evolution of light 

 from the crystals formed is so powerful, that a dark room 

 is thoroughly lighted. 



When the hot solution of arsenious acid is allowed to 

 cool rapidly, so as to deposit a pulverulent mass of arsenious 

 acid, little or no light is developed. The same happens 

 when the glassy acid is treated with nitric or acetic acid, 

 because these acids dissolve very little arsenious acid. A 

 faint light is observed with sulphuric acid. When a great 

 quantity of arsenious acid is treated with aqua regia, a 

 strong light appears during cooling. 



Rose explains this phenomenon by stating, that there 

 are two isomeric forms of arsenious acid, one translucent 

 and glassy, the other opaque and like porcelain. In each 

 of these states the acid has a different specific gravity, and 

 a different solubility in water. He conceives that by the 

 action of the acid in the case detailed, the glassy acid is 

 changed into the opaque state ; and that by the formation 

 of the new substance in a crystalline form the appearance 

 of light is produced.. 



This would require further investigation, because the 

 vol. m. v 



