RECHXT WORK IX AGRICULTURAL SCIENCE. 



CHEMISTRY. 



A new method for the determination of sesquioxids in phos- 

 phates and superphosphates, von Geiieber {Eine nene Methode/iir 

 die Bcatimmnngen dcr tScsquioxyde in Phosphaten und Superphosphaten. 

 Goslar: J. Jdyer c(; Sohn, 1896, pp. 7; Ztsclir. angew. Chem., 1896, N'o, 

 24, pp. 741, 742). — It is stated ou the basis of a number of analyses 

 reported that the Glaser method for the determination of sesc^uioxids iu 

 jihosphates is sufficiently reliable for ordinary purposes, but it has the 

 disadvantage of not distinguishing between the oxids of iron and 

 alumina. To overcome this objection the author proposes the follow- 

 ing method: Mix 10 gni. of crude phosphate or superphosphate in a 

 porcelain dish with 150 cc. of water and 20 cc. of concentrated hydro- 

 chloric acid, cover the dish with a watch glass, aiul warm in a water 

 bath until the ])hosphates are dissolved. Evaporate to dryness, take 

 up with hydrochloric acid and water, warm until redissolved, and wash 

 into a 500 cc. flask. When cool fill the flask to the mark, mix thor- 

 oughly, and Alter off aliquot parts for the determinations. 



For the determination of alumina, heat 50 cc. of the tiltrate (corre- 

 sponding to 5 gm. of substance) iu a 200 cc. flask, add 20 per cent 

 sodium hydrate solution until a slight precipitate appears, then add 30 

 cc. of the soda solution, heat to boiling, and allow to stand for 10 

 minutes in a warm jjlace, with frequent shaking. Cool, All the flask to 

 the mark, shake thoroughly, and filter off 100 cc. of the solution into a 

 beaker. Acidulate this solution slightly, heat to boiling, add a slight 

 excess of ammonia, and boil again. Filter off the phosphate of alumina, 

 wash thoroughly, dry, ignite, and weigh. Multiply the weight of sub- 

 stance obtained by the factor 41.8. 



For the determination of iron, place 100 cc. of the hydrochloric acid 

 solution in a 250 cc. flask, add some pure zinc, a little dilute sulphuric 

 acid, and allow to stand about 1 hour in a warm place in order to reduce 

 the iron oxid. Cool, fill the flask to the mark, and filter oft" 50 cc. of 

 the solution into a beaker containing 50 cc. of 20 per cent sulphuric 

 acid and 200 cc. of water, and titrate with permanganate solution. A 

 second, third, and even fourth titration may be made in the same 

 solution. 



Determinations are reported which show that the method gave 

 results closely agreeing with the theoretical percentages in a phosphate 



559 



