Carbonic Acid by Saline Solutions. 



487 



three experiments were made with portions of one and the same solu- 

 tion ; for the last two a fresh solution (prepared, to all appearance, 

 in exactly the same way as the previous one) was used. The differ- 

 ence in the results obtained show the precarious nature of the com- 

 bination : 



Two experiments were made with a solution prepared as follows : 

 The quantity of sulphuric acid necessary for the formation of 12*3 

 grammes crystallized sulphate of magnesia was diluted to a litre, and 

 pulverized carbonate of magnesia suspended in it. Although the mixture 

 was allowed to stand over night, shut off from the influence of the 

 atmosphere, the solution was still exceedingly acid. It is Well known 

 that carbonate of magnesia is difficultly soluble in cold dilute acids. To 

 have heated the solution would have frustrated the object of the experi- 

 ment, which was, by bringing nascent sulphate, of magnesia together 

 with nascent carbonic acid at ordinary temperatures, to give them the 

 best opportunity of combining. 



Two experiments were made with a similarly prepared solution of sul- 

 phate of lime. In this case sulphuric acid was added to the water in 

 quantity sufficient to form, with lime, more salt than was necessary for 

 the production of a saturated solution of gypsum. Here neutralization 

 took place without difficulty, and, as might have been expected, the 

 amount of carbonic acid formed was considerably greater than in the 

 case of the magnesia salt. 



Two experiments were made with an ordinary sulphate-of-magnesia 

 solution containing 2-05 grammes crystallized salt per litre. 



Two further experiments were made with a solution containing 2-05 

 grammes sulphate of magnesia and 20 grammes chloride of sodium per 

 litre. All were conducted in the way described above, and the results are 

 given in the following Table. The experiments with the carbonates of 

 magnesia and lime were made at a considerably later date than the 

 others ; the value of 10 c. c. baryta- water had in consequence become 

 equivalent to 32 c. c. instead of 32-34 c. c. oxalic acid. 



