RECENT WORK IN AGRICULTURAL SCIENCE. 



CHEMISTRY. 



The estimation of alumina and ferric oxid in natural phosphates, 



F. P. Veitch {Jour. Amer. Chem. Soc.,2^{1900), No. 5, pp. ^6-258).— 

 This article discusses the sources of error in older methods, reports the 

 results of a stud}^ of the various factors influencing the accurac}^ of the 

 determinations, and describes the following method, based upon the 

 results of these experiments: 



"Treat 1 gm. of substance in a platinum dish with from 5 to 10 cc. hydrofluoric 

 acid, let stand in the cold from 2 to 3 hours, heat on the water bath to complete 

 dryness, add 2 cc. concentrated sulphuric acid, running well around the sides, and 

 heat at a low temperature until the substance no longer flows in the dish. By this 

 process fluorin is completely expelled. Cool and add from 10 to 20 cc. concentrated 

 hydrochloric acid, and warm a few minutes to soften the mass; transfer to a small 

 beaker, and boil until all aluminum compounds are surely dissolved ( 15 to 30 minutes ) ; 

 filter from undissolved residue, if any, vi^ashing the filter thoroughly, add 50 cc. 25 

 per cent ammonium chlorid solution and ammonia until alkaline, then hydrochloric 

 acid until the precipitate just dissolves. Cool, dilute to about 250 cc, and add 50 per 

 cent sodium thiosulphate solution, drop l)y drop, until the solution is colorless, adding 

 in all 20 cc. ; cover with a watch glass, boil half an hour, tilter, wash back into the 

 same beaker, and dissolve in boiling hydrochloric acid; reprecipitate exactly as before, 

 after adding 2 cc. of a 10 per cent ammonium phosphate .solution. Wash 20 times 

 with 5 per cent ammonium nitrate solution, and ignite to constant weight. For the 

 second precipitation ammonium thiosulphate may also be used, but it is not strictly 

 necessary." 



A ne^w method for the determination of aluminum, E. T. 



Allen and V. H. Gottschalk {Amer. Chem. Jour., i34- {1900)., No. 4, 

 2)2>. '292-30 Jf). — The method proposed is as follows: 



"Dissolve the substance in which the aluminum is to be determined in water or a 

 mineral add. In case the latter is used, nearly neutralize with ammonia. Now dis- 

 solve a stick of potash in which the silica, iron, and alumina are known, in a meas- 

 ured (]uantity of water, and mix thoroughly. One to two grams of potash should be 

 sufficient. Pour the potash solution into a burette, and thence introduce into the 

 aluminum solution a quantity of the former, sufficient to redissolve the precipitate 

 which first forms. If the solution is still turbid no harm is done, but any consider- 

 able excess of potash should be avoided. [Soda] may be used as we! I as potash. Now 

 pass a stream of carbon dioxid into the solution. If the alkali is not in too great 

 excess, precipitation begins in a minute or two. Twenty minutes should suffice to pre- 

 cipitate 0.200 gm. AI2O3. The bulk of the alumina comes down in a few minutes, and 

 filtration then proceeds without difficulty. Transfer the precipitate for the most part 

 to a 9 cm. filter and wash several times without suction. The soluble impurities are 

 now mostly removed. Break the paper with a stirring rod, wash back completely 

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