CHEMISTRY. 371 



barium oxalate in au acid solutiou aud subsequently of iron and alu- 

 mina by the addition of a, slight excess of ammonia. 



The following directions for applying the method to the examination 

 of fertilizers are given : With superphosi)hates 10 gm. of the material 

 is mixed with 50O cc. of water and an amount of a solution of oxalate 

 of barium in hydrochloric acid (5 cc. of acid of 1.19 sp. gr. to each 7 

 gm. of oxalate) corresponding to 15 gm. of oxalate of barium. The 

 solution is then boiled vigorously for 20 minutes, hydrogen peroxid 

 added to oxidize the ferrous oxid, and finally a slight excess of ammonia 

 added. It is cooled, made u}) to a detinitc volume (1 liter ?), and filtered. 

 An aliquot part is evaporated, the residue ignited, taken up in hot 

 water, filtered if necessary, and 1 to 2 drops of hydrochloric acid and 

 the uecessary amount of platinum clilorid added. In some cases the 

 ignited residue may be at once dissolved in hydrochloric acid and 

 treated with platinum ehlorid. 



Witli Ivainit the proportions used are 10 gm. of the pulverized salt 

 and an amount of the reagent corresponding to 10 gm. of oxalate of 

 barium. 



The method was tried on a large number of substances containing 

 potash, and gave concordant and accurate results, and i»roved to be 

 easy of manipulation. For very impure products it seemed to possess 

 special advantages. 



The reactions Avhich take place in this method are thus explained: 

 The hydrochloric acid decomposes the oxalate of barium, forming bari- 

 um chlorid and free oxalic acid. The barium chlorid precipitates the 

 sulphuric acid present and all the bases pass into solution as chlorids. 

 The i)recipitatiou of suli)huric acid taking place in an acid solution is 

 free from potash. Only enough of the barium chlorid to precipitate 

 the sulphuric acid is decomposed. At the same time there is just 

 enough oxalic acid present to combine with bases previously united 

 with sulphuric acid and with the barium of the unused barium chlorid. 

 Wheu ammonia is added to a distinctly alkaline reaction, all chloiiu 

 combines with ammonia and the alkaline earths are precipitated as oxal- 

 ates, the iron and alumina as hydroxids. The chlorids of alkalies remain 

 in solution. lu the presence of an excess of ammonia the solution may 

 contain- small amounts of the oxalates of barium and magnesia, but 

 these are removed when the solution is subsequently evaporated to 

 dryness, ignited, taken up m water, and filtered. 



The estimation of potash in manures, V. Edwards and E. W. T. 

 Jo^ES {Cherii. Xeic.s, 70 {ls9i\, Xo. 1817, p. 140; No 1819, p. i7^).— The 

 essential features of Edwards' method, which is claimed to be less 

 " troublesome and tedious " than the ordinary text-book methods, are 

 as follows: One gram of the substance is charred (if it contains much 

 organic matter) and boiled w^ith water containing a few drops of hydro- 

 chloric acid. The solution thus obtained, purified by precipitation 

 with aminoiiia au(l arainonium oxalate, is evaporated to dryness with a 



