RECENT WORK IN AfxRICULTURAL SCIENCE. 



CHEMISTRY. 



Thomas slag and the determination of its phosphoric acid con- 

 tent, A. N. Papez {Ztschr. Lanchv. Versuchio. Oesterr.^ 3 {1900)^ j)P- 

 C95-71S; ahs. in Chem. Centhl., 1900, IT, Ko. '21^, p. /j^/5).— The 

 author made comparative tests of methods of determining solubilit}" in 

 citrate solution, citric acid, and formic acid, as well as of determining 

 total phosphoric :icid. The results with citi'ate solution are considered 

 unreliable. Those with citric acid and formic acid solutions were 

 more satisfactory. For preparing the solution for the determination 

 of total phosphoric acid the author recommends boiling 0.5 gm. of the 

 slag with 100 cc. of nitric acid of specific gravity 1.25 for 15 to 20 

 minutes. The phosphoric acid may be precipitated by means of the 

 ordinar}^ the Wagner, or the concentrated molybdic solutions. The 

 use of different kinds of magnesia mixture did not affect the results. 



The determination of potash by means of phosphomolybdic 

 acid, Wavelet {Ann. Chim. Analyt. et Appl., 5 {1900). jp- 289-'29'2; 

 ah. in Chem. Cenibl.. 1900, II, No. W, j). 6^95).— The directions 

 given are as follows: Dissolve 10 gm. of the substance in 200 cc. of 

 water and to 20 cc. of this solution add an excess of the molybdic solu- 

 tion (prepared as described below), evaporate to dryness on the water 

 bath, grind the residue to a powder, add 40 cc. of nitric acid (1 to 10), 

 heat on the water ])ath, and filter after cooling. Wash the precipitate 

 thoroughly with dilute nitric acid, dissolve in ammonia, and determine 

 phosphoric acid in the solution by means of magnesia mixture in the 

 usual way. Potash is calculated l)y multiplying the weight of the 

 magnesium pyrophosphate by 0.64. 



The potash may also be determined by titrating the ammonium- 

 magnesium phosphate with lead nitrate. For this purpose dissolve the 

 precipitate on the filter in 20 cc. of nitric acid (1 to 20), add phe- 

 nolphthalein and neutralize with ammonia, add 1 cc. of acetic acid, 

 make the volume to 100 cc, and to 50 cc. of this solution add 5 cc. of 

 5 per cent sodium acetate solution, and 3.5 per cent lead nitrate solu- 

 tion until a drop of the solution gives a yellow coloration with potas- 

 sium iodid solution. A blank test is made for correcting the results. 



713 



