CONVENTION OF OFFICIAL AGRICULTURAL CHEMISTS. 321 



determination of moisture in kainit "simply confirm our previous 

 experience and show how unsatisfactory our present official method 

 is." The referee suggested that an arbitrary method of procedure be 

 adopted for this determination, and proposed the heating of 2 gm. of 

 substance at 130° C. in an oil oven for 10 hours, the loss in weight to be 

 considered as moisture. This recommendation was referred to the 

 referee for next year for further study. 



A paper by M. G. Douk reported Experiments on the Volumetric 

 Estimation of Potash as Phosphomolybdate. Trials of the Wavelet 

 method (E. S. R., 12, p. 713) gave results which were too low and 

 quite irregular. To avoid the difficulties of this method and to make 

 it more generally applicable, the author worked out a method for 

 titrating the yellow precipitate, which he described in seme detail. 

 The results of a few comparative trials with the official method are 

 reported. u The method is exceedingly rapid and easy of execution, 

 necessitating no operation by which loss of potash is liable to occur.'' 



Recommendations. — The recommendation of the referee that the 

 sodium-hydrate method, which has been tried for two years with fav- 

 orable results, be adopted by the association was followed, but the 

 method can not be made official until the next year's meeting. The 

 method as suggested is as follows: Boil 10 gm. of the sample with 300 

 cc. of water plus 5 cc. of hydrochloric acid for 30 minutes; add a few 

 drops of phenolphthalein and carefully neutralize with sodium hydrate 

 free from potash, avoiding a large excess; add sufficient powdered 

 ammonium oxalate to precipitate all the lime; cool, dilute to 500 cc, 

 mix and pass through a dry filter, then proceed as in the Lindo- 

 Gladding method. 



PHOSPHOKIC ACID. 



C. B. Williams, referee, in the report on this subject, dealt mainly 

 with the question of the proper basis for valuation of phosphatic 

 fertilizers, particularly slag. The results for total phosphoric acid 

 on 3 samples of slag were quite concordant in the case of the same 

 analyst using the same method of solution, but there was often con- 

 siderable variation between the results of different anatysts, and 

 between the results of the same analysts using different solvents. 

 In the case of available phosphoric acid there was also considerable 

 variation between workers by the same method and on the same sam- 

 ple. The ammonium chlorid citric acid method and the cane sugar 

 citric acid method were the two methods which acted most energet- 

 ically upon the slag, but as no data were obtained from either field or 

 pot tests, it was impossible to say which of the solvents came nearest 

 to representing what different plants would be able to take up from 

 the soil in an average season. 

 11584— No. 4—04 2 



