120 



that the sodium peroxid fusion method for total phosphorus gives good results, but 

 the manipulation presents some difficulty, and the time required for making the deter- 

 minations is a disadvantage; third, that the magnesium nitrate method gives uni- 

 formly as good results for total phosphorus as the sodium peroxid fusion, and is quick 

 and easy of manipulation. With these facts in view, the referee would make the 

 following recommendations: 



(1) That the modified J. L. Smith method for total potassium be adopted as an 

 optional method of this association. 



(2) That the sodium peroxid fusion for total phosphorus be adopted as an official 

 method. 



(3) That the magnesium nitrate method for total phosphorus be adopted as a pro- 

 visional method of this association and be further tested. 



REPORT ON THE DETERMINATION OF CALCIUM CARBONATE IN 



SOILS. 



By JACOB G. LIPMAN, Associate Referee. 



Systematic determinations of calcium carbonate in cultivated soils seem highly 

 desirable in view of its important functions in crop production. Unfortunately, there 

 is no unanimity of opinion among chemists as to the methods best adapted for this 

 work. When the proportion of calcium and magnesium carbonates exceeds 1 per 

 cent, fairly accurate determinations may be made by the liberation of carbon dioxid 

 and its absorption and weighing in potash solutions. But when the proportion of 

 carbonate is small, as is true of so many of our soils, the quantity of carbon dioxid 

 which remains in solution in the acid is very large in proportion to its entire amount. 

 This source of error has frequently been commented upon and has led to several 

 more or less successful attempts to correct it." 



The associate referee on soils thought it advisable, therefore, to outline some cooper- 

 ative work on one or two promising methods for the determination of carbonates in 

 soils. Samples of two different soils were sent to eleven members of the association 

 who had signified their willingness to cooperate in the testing of soil-analytical meth- 

 ods. It was suggested that determinations of carbonates be made in the samples by 

 Knorr's method as described in Wiley's Agricultural Analysis, b Where possible, the 

 results secured by Knorr's method were to be checked by the method described by 

 Amos in the Journal of Agricultural Science, c 



The samples were sent out early in September, and analyses were made and reported 

 by W. B. Ellett of the Virginia station, by Percy E. Brown of the New Jersey station, 

 and Ernest Van Alstine of the Illinois station. Mr. Van Alstine's data were trans- 

 mitted to the associate referee by Mr. Hopkins. 



Mr. Ellett and Mr. Brown used Knorr's apparatus for the determination of the car- 

 bon dioxid. Mr. Van Alstine employed the method regularly used at the Illinois 

 station and consisting of the liberation of the carbon dioxid "by boiling with hydro- 

 chloric acid and ascertaining the quantity of carbon dioxid evolved by measuring 

 before and after absorption by a caustic potash solution," The results were as follows: 



a See Hall and Russel, A Method for Determining Small Quantities of Carbonates, 

 Transactions, J. Chem. Soc., London, 1902, 81: 81. 

 &Vol. 1, p. 338. 

 c 1905, 7:322. 



