1 ^ Dr. Ure on Chloride of Lime. 



judicious plan, as the hydrate advances in impregnation, its 

 faculty of absorption becoming diminished, it would be requi- 

 site to diminish proportionately the evolution of chlorine, or to 

 allow the excess to escape, to the great loss of the proprietor, 

 and, what is of more consequence, to the great detriment of the 

 health of the workmen. 



The manufacturer generally reckons on obtaining from one 

 ton of rock-salt, employed as above, a ton and a half of good 

 bleaching powder. But the following analysis of the operation 

 will shew, that he ought to obtain two tons. 



Science has done only half her duty, when she describes the best 

 apparatus and manipulations of a process. The maximum produce 

 should be also demonstrated, in order to shew the manufacturer 

 the perfection which he should strive to reach, with the minimuvi 

 expense of time, labour, and materials. For this end I instituted 

 the following researches. I first examined fresh commercial 

 specimens of bleaching-powder ; 100 grains of these, afforded 

 from 28 to 22 grains of chlorine. This is the widest range of 

 result, and it is undoubtedly considerable ; the first being to 

 the second, as 100 to 78.6. The first yielded, by saturation 

 with muriatic acid, 82 grains of chloride of calcium, equi- 

 valent to about 41 of lime; it contained besides 26 per cent. 

 of water, and a very little common muriate ready formed. On 

 heating such powder in a glass apparatus, it yielded at first a 

 little chlorine, and then oxygen tolerably pure. The bulk of 

 chlorine did not exceed one-tenth of the whole gaseous pro- , 

 duct. Of the recently prepared powder of another manufac- 

 turer, 100 grains were found to give, by solution in acid, 23 

 grains of chlorine, and there remained, after evaporation and 

 gentle ignition, 92 grains of muriate of lime, equivalent to 

 about 46 of lime. Supposing this powder to have been nearly 

 free from muriate, (and the manufacturers are anxious to pre- 

 vent the deliquescent tendency which this introduces,) we should 

 have its composition as follows : 



Chlorine .23 3.5 



Lime . . 46 one atom 3.5 x 2=7.0 

 Water . . 31 



100 



