22 Dr. lire on Chloride of Lime. 



muriate of lime protects the surface of the metal, almost com- 

 pletely, from the gas. With an apparatus of this kind, (which 

 indeed is the same as that which! have long used for analyzing 

 limestones and marles, (see article Carbonate, in my Chemical 

 Dictionary,) I get good accordances, with the results derived 

 from the loss of weight, suffered by a like quantity of the 

 chloride, when it is dissolved in dilute muriatic acid. Since a 

 cubic inch of chlorine may be estimated in round numbers at 

 f of a grain, we may expect 10 grains of bleaching-powder to 

 yield from 3 to 4 cubic inches of that gas ; or by weight, from 

 20 to 30 per cent., a wide range of power, which it is well 

 worth the bleacher's or paper-maker's while to ascertain. If 

 carbonic acid be suspected, we need only agitate the mercury 

 through the gas, adding some of the metal, from time to time, 

 as the absorption proceeds. The carbonic acid will remain, un- 

 condensed at the top, and may be estimated in the usual way. 



Sulphate of indigo, largely diluted with water, has been long 

 used, for valuing the blanching power of chloride of lime ; and 

 it affords, no doubt, a good comparative test, though from the 

 variableness of indigo it can form no absolute standard. Thus 

 I have found, 3 parts of indigo from the East Indies, to satur 

 rate as much bleaching-powder, as 4 parts of good Spanish 

 indigo. 



M. Welter's method is the following : — He prepared a solu- 

 tion of indigo in sulphuric acid, which he diluted, so that the 

 indigo formed -^-^ of the whole. He satisfied himself by ex- 

 periments, that 14 litres (854.4 cubic inches, or 3.7 wine gal- 

 lons, English,) of chlorine, which weigh 651i English grains, 

 destroyed the colour of 1 64 litres of the above blue solution. 

 He properly observes, that chlorine discolours more or less of the 



125.6 grains were obtained, which, by calcination, became 84.3, having 

 thus lost 41.3 grains. But 41.3 — ii±iI-=39.65= lime present, nncom- 

 bined with muriatic acid. And 41.3 x 1.7=70.2= the carbonate of lime 

 in the residuary 84,3 grains of calcined salts. Therefore, 84.3 — 70.2= 

 14.1= muriate of lime. Now, by dissolving out the muriate of lime, and 

 evaporating, I got 14 grains of it, and the remaining carbonate was 70.3 

 grains. Hence this powder consisted of, chlorine, 21; lime, 3D.65 ; mu- 

 riate of lime, 14, and water 25.35=100. 



