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



Laboratory in the University of Edinburgh, and I gladly avail myself of 

 this opportunity to thank them both. 



The analytical series consisted of experiments on solutions of the 

 different salts saturated with carbonic acid. A certain quantity of each 

 was distilled almost to dryness, the steam being condensed in an ordinary" 

 Liebig's condenser, to which was fitted a tubulated receiver, having a 

 bulbed Y-tube attached containing baryta-water. The distillation was 

 interrupted and the baryta-water changed after the passage of every 

 eighth of the distillate, the amount of carbonic acid passed being roughly 

 estimated by the apparent turbidity of the baryta- water. The object of 

 these experiments being to find out which of a number of saline solutions 

 had the property of retaining carbonic acid, and to ascertain roughly what 

 length of time one must boil in order thoroughly to expel it, an accurate 

 determination of the carbonic acid actually passing during the intervals 

 would have been superfluous. Besides these, a number of quantitative 

 determinations were made of the amount of carbonic acid actually 

 absorbed by different solutions. 



The synthetical series consisted of experiments for the determination 

 of the absorption-coefficients of two solutions the one of sulphate of 

 magnesia, the other of sulphate of lime. 



Let us take the analytical series first. As before remarked, it is sub- 

 divided into two sets, which we shall treat in their order. In the one 

 observations were made on the elimination of the -carbonic acid as the 

 distillation proceeded ; in the other an attempt was made to determine 

 how much carbonic acid, in a saline solution saturated with the gas, was 

 actually retained or bound, or at least kept from freely exercising its 

 properties as a gas, by the presence of the salt in the solution. 



First Experiment. In order to have a certain standard of comparison 

 in judging the retardation caused by salts in the escape of carbonic acid 

 from solutions on boiling, distilled water was saturated with the gas and 

 distilled in the manner indicated above. During the passage of the first 

 eighth of distillate the gas evolution was of course abundant, during the 

 second a perceptible quantity passed, after which no more could be de- 

 tected. It may be assumed, then, that, in the experiments which followed, 

 the carbonic acid held simply in solution by the water passes almost 

 entirely in the first eighth part of the distillate, and that whatever 

 passes afterwards has been retained, in some way or other, by the salt 

 in solution. In conducting these experiments no baryta-water was 

 put in the receiver itself, but only in the Y-tube. The water collected 

 was always tested with baryta-water, and with the general result that 

 in the first fraction carbonic acid was present in abundance, while in 

 the latter ones there was rarely a trace to be detected. That the dis- 

 tillate consisting of pure water should contain not a trace of the gas, 

 whose presence in the atmosphere above it is attested by the precipitate 



