108 EXPERIMENT STATION RECORD. 



a volume of 2 liters. In case of the latter solution 40 cc, corresponding to 10 

 gm. of citric acid, is used. 



The separation of silicic acid in the determination of citric-acid soluble 

 phosphoric acid, J. HasenbXumer {Chem. Ztg., SO {1906), No. 53, pp. 665, 666; 

 abs. in Cheni. Ccntbl., 1906, II, No. 6, p. 556). — Investigations with a number 

 of different kinds of Thomas slag are reported which show that tbe higher 

 results obtained when silicic acid is not previously removed from the solution 

 are not due to tbe presence of tbis substance in the precipitate, and indicate 

 that tbe discrepancy may be due eltber to tbe carrying down of a certain amount 

 of phosphoric acid in the gelatinous silicic acid when this is removed before 

 precipitation or to the fact that tbe precipitate obtained after removal of the 

 silicic acid is different in composition from that produced before such removal. 



The use of compressed air in analysis of superphosphate, G. Schliebs 

 {Cliem. Ztg., SO {1906), A'o. JT, p. 5S'i). — Good results are reported in the 

 substitution of agitation by means of a stream of compressed air in place of 

 mechanical agitation. 



The determination of potash in potash salts and mixed fertilizers by 

 the Neubauer modification of the Finkener method, M. Kling and O. Engels 

 {Ztfivlu: AnaJiit. Chcui.. ',5 {1906), No. 5-6. pp. 315-332; abs. in Analyst, 

 31 {1906), No. 365, pp. 273, 21',; Chem. Centbl., 1906, II, No. .',. p. 360).— The 

 authoi's have used the following modification of the Finkener-Neubauer method 

 with satisfactory results : 



Dissolve 10 gm. of the potash salt in 500 cc. of water, and to 25 cc. of this 

 solution, corresponding to 0.5 giu., add a few drops of hydrochloric acid, tbe 

 necessary platinum chlorid, and evaporate to dryness in a porcelain dish. 

 Take up with water and alcohol as in Neubauer's method, collect on a Neubauer- 

 Gooch crucible, wash with alcohol, and dry by placing the crucible on a 

 moderately hot metal plate. 



Reduce the platinum salt in a current of coal gas, heating for the first 10 

 minutes over a very low flame, and finally at a faint red heat for 20 minutes. 

 When reduction is complete heat tbe crucible for 2 minutes over the naked flame 

 of a Teclu burner, wash tbe contents of the crucible about 15 times with hot 

 water and 2 or 3 times with cold 15 per cent hydrochloric acid, immerse the 

 crucible to about three-quarters of its height in nitric acid of the same strength 

 in a porcelain dish, cover the dish with a clock-glass, beat for about 30 minutes 

 on the boiling water-bath and allow to cool. Finally wash the platinum in the 

 crucible with hot water and alcohol, ignite, and weigh. 



In case of mixed fertilizers, shake 20 gm. of the sample with 800 cc. of water 

 for 30 mituites in a liter flask, make up to the mark, and filter. To 100 cc. 

 of the filtrate, corresponding to 2 gm., add ammonia and ammonium carbonate 

 in a 200 cc. flask, make the volume to 200 cc, and filter and evaporate 50 cc, 

 corresponding to * gm. of materia' to dryness in a platinum dish. Dry 

 the residue, drive off ammonium salts, and ignite to fusion, taking up the fused 

 residue with hot water and a little hydrochloric acid. Filter if there is an 

 insoluble residue. Add platinum chlorid solution (2 cc. of a 10 per cent solu- 

 tion is usually suflicient), evaporate to dryness, and determine potash as 

 described above. 



The accuracy of the method was tested by a number of determinations and 

 it was shown that the i)resence of i)liosphates does not interfere with the 

 determination. A table for calculating tbe amount of potash from the weight 

 of platiiunn ol)tained from 0.5 gm. of substance (factor=0.4S10S) is given. 



On the determination of potash by means of platinum hydrochlorid in the 

 presence of sulphates of the alkalis and alkaline earths, K. Kegel {Chem. 



