(2) _Estimation of Potash in Guanos and Other Fertilizers containing Organic Substances._—Ten grams of the substances are carefully incinerated at a low temperature in a platinum dish. After ignition the contents of the dish are placed in a half liter flask and boiled for an hour with hydrochloric acid and a few drops of nitric acid. The sulfuric acid can then be precipitated directly with barium chlorid, or better, allow the flask to cool, fill to the mark, filter and treat an aliquot part of the filtrate with barium chlorid as described above. The filtrate from the separated sulfate of barium is neutralized with ammonia and all the bases, with the exception of magnesia and the alkalies, precipitated with ammonium carbonate; boil, fill to the mark and filter. Of this filtrate evaporate from 100 to 200 cubic centimeters in a platinum dish. After evaporation the ammonium salts are driven off by careful ignition, the residue taken up with hot water and filtered through as small a filter as possible into a porcelain dish; the magnesia remaining in the precipitate. The filtrate is acidified with a few drops of hydrochloric acid, ten cubic centimeters of platinic chlorid added and the further determination conducted as with kainit. =256. Dutch Method.=—The process used at the Royal Agricultural Station of Holland is almost identical with that employed at Halle.[205] A. _Method for Stassfurt and other Potash Salts._—The necessary reagents are: 1. A dilute solution of barium chlorid: 2. A solution of platinic chlorid containing one gram of platinum in ten cubic centimeters: It must be wholly free from platinous chlorid and nitric acid, and partially freed from an excess of hydrochloric acid by repeated evaporations with water. 3. Alcohol of eighty per cent strength by the volume: The methods of bringing the potash into solution and of precipitating the sulfuric acid are the same as for the Halle process described above. Add then twenty cubic centimeters of the platinum solution and evaporate the mixture nearly to dryness. Add a sufficient quantity of eighty per cent alcohol and stir for some time. Allow to stand and then filter through a gooch dried at 120°. Finally wash with eighty per cent alcohol, dry at 120°, and weigh. B. _Method for Potash Superphosphate and other mixed Fertilizers._—The reagents necessary are the same as under A, and, in addition, a saturated solution of barium hydrate and a solution of ammonium carbonate mixed with ammonia.