Carbonic Add by Saline Solutions. 485 



in the exit-tube, shows that, at feeble pressures, the solution of carbonic 

 acid requires considerable time for its completion. 



Second Experiment. A chloride-of-sodium solution containing 2 per 

 cent. Na Cl had a strong stream of C0 2 passed through it for about ten 

 minutes and was then distilled. During the passage of the second* 

 eighth there was still a considerable quantity, during that of the third a 

 very slight trace, and after that none. 



Third Experiment. A chloride-of-magnesium solution containing 0'25 

 per cent. Mg C1 2 was treated in the same way as the chloride-of-sodium 

 solution, when the whole of the C0 2 passed in the first fraction. 



Fourth Experiment. A solution containing 4 per cent. Mg C1 2 and 10 

 per cent. Na Cl was saturated with CO 2 and allowed to stand in a closed 

 vessel over night. On distilling, it was found that carbonic acid con- 

 tinued to be given off in perceptible but gradually decreasing quantities 

 until the end. 



Fifth Experiment. For this and the three following experiments a 

 solution containing 12-3 grammes crystallized sulphate of magnesia (in 

 a litre?) was used. Carbonic acid was passed through some of this 

 solution for about 10 minutes, and the liquid allowed to stand in a 

 closed vessel over night. On distillation 'there passed during the second 

 fraction very little, during the third and fourth fractions decidedly 

 more, during the fifth again much less, and afterwards, to the end, slight 

 but perceptible traces of carbonic acid. 



Sixth Experiment. The solution was heated to nearly boiling, and CO 2 

 passed into it until it was cold, the whole being allowed to stand over 

 night. During the passage of the second, third, fourth, and fifth frac- 

 tions, the amount of gas was about constant and small. It increased 

 greatly during the sixth, falling away again during the seventh. 



Seventh Experiment. The conditions were exactly the same as those 

 of the fifth experiment ; and the results in the two cases agreed well with 

 each other, the amount of gas coming off increasing slightly about the 

 middle of the operation'. In order to see if the rise of temperature con- 

 sequent on concentration had any thing to do with the phenomena under 

 consideration, a thermometer was immersed in the boiling liquid. It read 

 at the end of the second, third, fourth, and fifth fractions 102-5, 102-9, 

 103, and 103-2 respectively. 



Eighth. Experiment. The conditions were the same as in the last, 

 only that the solution stood two days before- distillation. In the re- 

 sults there was this peculiarity, that in the fourth fraction the car- 

 bonic acid disappeared altogether, reappearing, however, again in the 

 fifth. 



* It is unnecessary in the cases where no means were taken to free the solution 

 from simply dissolved carbonic acid to repeat in each one that the first fraction con- 

 tained abundance. 



2r2 



