142 



Journal of Agricultural Research 



Vol. XII, No. 3 



Table I. — Effect of carbon dioxid on the reaction of soil suspensions 



o Mercury cell, with mercuric chlorid and potassium chlorid in Nlio concentration 



Since the measurement of the H-ion concentration is based on hydrogen 

 at atmospheric pressure, any diminution in this pressure caused by the 

 admixture of carbon dioxid would result in a certain lowering of the 

 electromotive force. Loomis and Acree (5) have determined the changes 

 in electromotive force resulting from the diminution of the partial pres- 

 sure of hydrogen within certain ranges. Their data indicate that these 

 changes are so slight as to be without significance in the present investi- 

 gation, hence no corrections for this factor have been made. Most of the 

 determinations reported above are the averages of duplicates. The 

 agreement of these duplicates was in nearly all cases within 0.005 volt. 



The data in the above table have to do with the efifect of carbon dioxid 

 on three general types of soil reaction. The acid type of reaction is 



