486 Mr. J. Y. Buchanan on the Absorption of 



Ninth Experiment. Sea-water from the Firth of Forth was distilled. 

 Here, as in the case of the sulphate of magnesia, the amount coming off 

 increased about the middle, falling away again in the fifth fraction. In 

 the sixth, however, it experienced a slight increase, falling off again 

 towards the end of the operation. 



From these experiments we may conclude that, alone and in the 

 degree of concentration in which they occur in the sea, the two most 

 abundant salts, namely chloride of magnesium and chloride of sodium, 

 exercise no retarding influence on the liberation of carbonic acid on boil- 

 ing. When mixed, however, as in the fourth experiment, they appear 

 to have this effect. Whether, if sufficiently diluted to represent sea- 

 water, they would continue to do so I was unable to ascertain, as the 

 investigation of the sulphates occupied all the time at my disposal. It 

 is further evident that, in the sulphate-of -magnesia solution experimented 

 on, we have a solution which behaves towards carbonic acid in the same 

 way as sea-water. 



Let us pass now to the second set of the analytical series namely, the 

 estimation of the amount of carbonic acid retained in consequence of the 

 presence of the salts in question. The apparatus used was the same as 

 that in the last set, baryta-water being contained both in the receiver 

 and in the V-tube. 



Experiments were made on solutions of sulphate of magnesia, of sul- 

 phate of magnesia and chloride of sodium, and of sulphate of lime, to 

 which were added some on sea-water itself. In every experiment the 

 quantity of solution operated on was 300 c. c. The carbonic acid 

 coming off was retained by baryta-water of known strength, the re- 

 maining free baryta being afterwards determined by means of oxalic 

 acid. Eosolic acid was used to determine the point of neutralization. 

 The oxalic acid was rather stronger than tenth-normal ; it contained 

 6-478 grms. C 2 H 2 4 + 2H 2 in the litre, 'which is equivalent to 2-259 

 grms. carbonic acid. 1000 c. c. baryta-water required 3235 c. c. oxalic 

 acid for neutralization. 



The method of conducting the operation was as follows : Carbonic 

 acid was passed through the solution until it could be assumed to be 

 saturated. Six to seven litre's of air were then drawn through it cold, 

 after which it was heated to boiling, and allowed to boil for from two to 

 three minutes in a current of air. The receiver with the baryta-solution 

 was then attached, and the distillation continued in a stream of air, 

 until the contents of the flask were nearly dry. The baryta-water then 

 remaining unneutralized was titrated, and from it the amount of carbonic 

 acid ascertained. 



Experiments on sulpliate-of-magnesia solution containing 12*3 grammes 

 crystallized salt per litre. As all were conducted in precisely the same 

 way, it will be sufficient to give the results in a tabular form. The first 



