1 4 Dr. Ure c?j Chloride of Lime. 



and subject this hydrate at the temperature of 50° to a stream 

 of chlorine, we can without difficulty condense, on 35.5 of lime, 

 45 of chlorine, and even somewhat more. Now this proportioa 

 should seem to form the true state of atomic saturation and re- 

 pose, for just as much chlorine is present as is capable of dis- 

 placing the whole of the oxygen from the calcium, and con- 

 verting the bleaching powder entirely into muriate of lime. The 

 intimate union, however, existing between the calcium and 

 oxygen, and the consequent close contact of their molecules, 

 must give the latter element a chemical advantage, so to speak, 

 over the more distant molecules of the chlorine, which seems 

 loosely clustered round the hydrate by the joint affinities of the 

 water and lime. It is owing to this looseness and feebleness of 

 combination which increase with the degree of impregnation, 

 that the slightest heat is then apt to restore elasticity to the 

 attached chlorine, as we have seen. In proportion, however, 

 as the mass of the hydrate increases, relative to the chlorine, it 

 exercises a more powerful attraction, draws the chlorine appa- 

 rently into closer combination, whence the adhesion of the 

 oxygen is impaired. For the atoms to take a new defiiiite ar- 

 rangement to the subversion of an existing one, there is re- 

 quired a certain energy of attraction, and that energy seems to 

 be counteracted in the present instance by the repulsion be- 

 tween the two vitreo-electric elements, oxygen and chlorine, 

 while the feebler affinity of the former for calcium is compen- 

 sated by proximity of contact, and thus it is enabled to hold 

 its place at low temperatures. Heat exalts the affinities be- 

 tween calcium and chlorine, and at the same time lends elas- 

 ticity to the oxygen. It is that feebleness of affinity between 

 the constituents of chloride of lime which leaves the quantities 

 of each indefinite, and makes it resemble rather a mixture, (or 

 at most a sahne solution,) than a true atomic compound. It is 

 in fact as indeterminate in its proportions as it is unstable in its 

 equilibrium. 



Of the Manufacture of Bleaching Powder. 

 A great variety of apparatus has been at different times con- 



