6 Dr. Ure on Chloride of Lime. 



am disposed," says he, " to ascribe this surplus of water to 

 some accidental exposure of the bleaching-powder to moisture 

 during a voyage from Belfast, where it was manufactured, to 

 Glasgow, where I analyzed it *." His new method of analysis, 

 which indeed had been indicated in his preceding paper, con- 

 sisted in subjecting the bleaching-powder to heat in a glass re- 

 tort, placed in a sand-bath. He thus converted the chloride 

 of lime into chloride of calcium, with the disengagement of 

 oxygen. This gas being received into graduated jars, filled 

 with water in the pneumatic trough, indicates by its volume the 

 quantity of chlorine employed in its extrication ; for each vo- 

 lume of oxygen corresponds, in this case, to two volumes of 

 chlorine. Hence, estimating the volume of chlorine present 

 at double the volume of oxygen evolved, and converting it into 

 weight, at the rate of 100 cubic inches to 76 J grains, the pro- 

 portion of chlorine associated with the calcareous hydrate, 

 comes to be known. On this process M. Gay Lussac observed, 

 that if the chloride of lime by any means passes into chlorate 

 and muriate, then the same bulk of oxygen would still be af- 

 forded, though now the powder would have entirely lost its 

 bleaching power. It is doubtful, however, if any chlorate of 

 lime be formed in this way, though common muriate is pro- 

 gressively generated, as Mr. Dalton justly remarked. The 

 matter which remains in the retort, consists of quicklime and 

 chloride of calcium, the latter of which, being separated by its 

 superior solubility in water, is evaporated to dryness and 

 weighed. His analytical conclusions are thus stated : " The 

 true constitution of the bleaching-powder, reduced to 100 parts, 

 is as follows : 



Subbichloride of lime (suboxymuriate of Mr. Dal- 



ci m r20.31 chlorine 

 *°" ^^-^Hsi-eOlime 



Muriate of lime 15.46 



Water 27.86 



Uncombined lime 4.77 



TOOM 



* Annah of Phil. XV., p. 405. 



