AGRICULTURAL CHEMISTRY AGROTECHNY. 207 



Where n equals the titer of the hydrogen peroxid solution, t the amount of 

 potassium permanganate in 1 liter, h the number of cubic centimeters of hydro- 

 gen peroxid usetl, and p the number of cubic centimeters of tenth-normal 

 potassium permanganate used, the percentage of manganese in the soil is as 

 follows : 



When the manganese content of the soil is very low, or when very great 

 accuracy is necessary, from 50 to 75 cc. of the filtrate can be concentrated to 

 30 cc, and after adding 20 cc. of concentrated nitric acid oxidation can be 

 accomplished with bismuth peroxid. The above concentrations must be changed 

 accordingly. 



Further investigations with reference to the extraction process (the effect of 

 cold, warmth, the use of hydrochloric acid or nitric acid, etc.) and the use 

 of the method for soils rich in lime and for plant ashes are to be made. 



Potash in mixed fertilizers, T. E. Keitt {South Carolina Sta. Bui. 17S 

 (1913), pp. 3-16).— Some of this material has been noted (E. S. R., 28, p. 508). 



The rendering insoluble of the potash when muriate of potash or kainit is 

 mixe<l with shig is due to the formation of a compound which is almost entirely 

 soluble in hydrochloric acid, sp. gr. 1.115. Some of the potash, as well as 

 silica, ammonia-precipitable substances, and lime was dissolved by citric acid 

 and ammonium citrate solution, sp. gr. 1.09. Potash was most soluble in the 

 ammonium citrate solution, and the remaining substances were most soluble in 

 the citric acid solution. Probably there is a substitution of the ammonia radical 

 for potassium in the compound. There was no definite relation between any 

 one of the other elements and the pota.sh dissolved by the same solvent. The 

 operation of separating the potash soluble in hydrochloric acid from other sub- 

 stances dissolved by the same solvent and precipitable by ammonia was found 

 to be very tedious. The separation, however, may be accomplished by using 

 large dilutions and making many precipitations. 



" Basing our work on the difficulty of separating the potash present from 

 the ' ammonia precipitate,' a study was made of the influence of the large 

 ' ammonia precipitate ' always present in the determination of potash in 

 mixed fertilizers by our Official Method for solution. 



" The results of this investigation show that there are two partially com- 

 pensating sources of error in our Official Method of solution : 



"(a) The volume is decreased by the bulk of the precipitate in the flask, 

 which would tend to increase the percentage of potash present. 



"(b) The potash is decreased by occlusion of potash by the heavy precipi- 

 tate formed on addition of ammonia and ammonium oxalate. These two sources 

 of error tend to balance to some extent. 



" It is impossible to wash out the potash occluded within the precipitate with 

 hot water. 



" The occluded potash can be separated to a certain extent by repeatedly dis- 

 solving the precipitate in hydrochloric acid, diluting to a volume of about 400 

 cc, precipitating with ammonia and ammonium oxalate, and filtering to deter- 

 mine potash in the filtrates. 



"The use of pure salts in making the solutions shows that both iron and 

 calcium phosphate, when precipitated with ammonia, occlude potash, and that a 

 combination of the two is even more effective to produce occlusion." 



The detection of org'anic poisons (toxins and the like) in food, G. Babgeb 

 (Pharm. Jour. [London], .',. ser., 37 {1913), No. 2609, p. 572).— A paper read at 

 the International Congress of Pharmacy at The Hague, 1913. 

 55733°— No. 3—14 2 



