58 



BY PNEUMATIC APPARATUS. 



The following representation and description will make tlie ope- 

 ration quite clear ; 



"A, B, C, D, E, represent the different parts of this apparatus. A repre- 

 sents the bottle for receiving the soil. B the bottle containing the acid,, 

 furnished with a stop-cock. C the tube connected with a flaccid bladder. 

 D the graduated measure. E the bottle for containing the bladder. When 

 this instrument is used, a given quantity of soil is introduced into A. B 

 is filled with muriatic acid diluted with an equal quantity of water ; and 

 the stop-cock being closed, is connected with the upper orifice of A, which 

 is ground to receive it. The tube C is introduced into the lower orifice of 

 A, and the bladder connected with it placed in its flaccid state into E, 

 which is filled with water. The graduated measure is placed under the 

 tube of E. When the stop-cock of B is turned, the acid flows into A, am! 

 acts flpon the soil ; the elastic fluid generated passes through C, into the 

 bladder, and displaces a quantity of water in E equal to it in bulk, and 

 this water flows through the tube into the graduated measure ; and gives 

 by its volume the indication of the proportion of carbonic acid disengaged 

 from 'the soil; for every ounce measure of which two grains of carbonate 

 of lime may be estimated." Davy's Agr. Chem. 



The correctness of this mode of analysis depends on two well- 

 established facts in chemistry : 1st, That the component parts of 

 calcareous earth always bear the same proportion to each other, and 

 these proportions are as 43.7 parts (by weight) of carbonic acid, to 

 56.3 of lime ; and, 2d, That the carbonic acid gas which two grains 

 of calcareous earth will yield, is equal in bulk to one ounce of fresh 

 water. The process, with the aid of this apparatus, disengages, 

 confines, and measures the gas evolved ; and for every measure 

 equal to the bulk of an ounce of water, the operator has but to 

 allow two grains of calcareous earth in the soil acted on. It is 

 evident that the result can indicate the presence of lime in no other 

 combination except that which forms calcareous earth ; nor of any 



