BARIUM CHLORATE. 345 



with free oxygen, others with potassium chlorate, found in three 

 trials that the excess of heat developed by 9 -75 grms. of 

 potassium chlorate amounted to 378, 326, and 341, respectively ; 

 or, taking the average, to 348 Cal., which would give for 



KC10 3 ( = 122-6 grms.) -h 4'37 Cal., 



a value subject to the doubts involved by such an indirect 

 determination. 



Finally, Thomsen 1 reduced a diluted solution of chloric acid 

 by means of sulphurous acid an operation which can be easily 

 carried out in a calorimeter ; on the other hand, he decomposed 

 potassium chlorate by means of the heat produced by the com- 

 bustion of hydrogen a process which does not seem to admit 

 of such accuracy as the former one. 



He deduced from his trials the following results : 



i[H 2 + C1 2 + 5 + water = H 2 0, C1 2 5 (diluted)], - 10-2 

 KC10 3 (solid) = KC1 (solid) + O 3 , + 9-8. 



2. The following are the results arrived at by the author. 

 Following the method he constantly adopted, he took, to start 

 with, a crystallised and definite salt, in preference to a titrated 

 solution, or a solution containing the acid prepared by precipita- 

 tion solutions whose composition is always less exact. 

 Barium chlorate was used, which was in very fine crystals, and 

 corresponded to the formula Ba(C10 3 ) 2 + H 2 0. Analysis of 

 this salt gave 



BaS0 4 H 2 



Found 72-2 5'7 



Calculated 72-3 5'6 



This salt, when dehydrated and then heated in a tube, is im- 

 mediately decomposed with a very marked incandescence, and 

 a kind of explosion which throws off to some distance a white 

 powder, consisting of barium chloride ; these effects are observed 

 even when only a few grammes of the dry salt are operated 

 upon. It is well known that analogous phenomena may be 

 observed with potassium chlorate, but barium chlorate exhibits 

 them to a far greater degree. This proves that its decomposition 

 is exothermal. 



3. A known weight, 2'5 grms., of this salt was dissolved, in 

 one case in 400 cc., in another in 900 cc. of water, and 

 reduced by means of 100 cc. of a moderately concentrated 

 solution of sulphurous acid. The barium chlorate is thus com- 

 pletely converted into barium sulphate and hydrochloric acid, 

 as was ascertained by various determinations. The reduction 

 is effected more rapidly according as the solution is less diluted, 

 all other things being equal. With 500 cc. of liquid, and 2'5 



1 " Journal fur Praktische Chemie," Band xi. s. 138. 1875. 



