164 CHEMICAL MANURES. 



There is run into a lead-lined vessel, fitted with an agitator, a 

 measured quantity of a 10 per cent solution of phosphoric acid, in 

 which a corresponding quantity of sulphate of potash is dissolved. 

 iVfterwards, whilst constantly stirring the mixture, but without heat- 

 ing, the calculated quantity of pulverized phosphatic chalk is slowly 

 incorporated. When, after about an hour, the conversion is accom- 

 plished, the phosphatic solution is separated from the residue by filter 

 presses, and the liquor evaporated to a pasty consistency by steam 

 heating. The dry salt is afterwards obtained, fit to be centrifuged 

 by drying it in a special chamber heated by steam at a temperature 

 of 70° to 80° C. From the filter presses, the residue falls directly 

 into a second mixing tank with agitator, likewise lined w4th lead, and 

 containing the quantity of sulphuric acid necessary to decompose 

 the phosphate. When this decomposition is complete, the residue 

 is separated from the liquid by means of the filter press, completing 

 the extraction this time by washing, for the wash water afterwards, 

 serves to dilute the sulphuric acid. The filtrate, which consists of a 

 mixture of phosphoric acid and potassic phosphate, flows from the 

 filter press directly into the first receiver-mixer. The product thus. 

 obtained contains 38 to 40 pet- cent of PoO^ almost entirely soluble 

 in water, 31 to 33 per cent K^O, in addition to a few per cents of 

 sulphuric acid, lime, etc. 



The Salz Werke Co., Neustassfurt, have likewise succeeded in 

 producing a pure and concentrated phosphate of potash from 

 potassium chloride. The experiments made by this company led 

 to quite an unexpected result. It is known that the metaphosphate 

 obtained by the decomposition of potassic chloride, by phosphoric, 

 acid, at the temperature of fusion, is by itself completely insolul^le 

 in water, and even in acids. Now it has been found that by cooling 

 it suddenly, it is converted into a modification very soluble in water. 

 The decomposition is effected in a muffle furnace for sulphate, the 

 evolved hydrochloric acid is condensed, and the liquid metaphosphate- 

 flows boiling from the oven direct on to cold plates, in a thin layer. 

 After crushing, the product forms a dry salt easily preserved and 

 containing 50 per cent P.jOj and 45 per cent K^O. x\lthough 

 phosphate of potash, and similar concentrated manures, have not 

 assumed, in agriculture, the importance that w^as at first anticipated,, 

 especially for cereal cultivation, they have none the less a great im- 

 portance in certain special cultures, and above all in the Colonies- 

 owing to freight charges, which are heavy. Their rational use in 

 horticulture likewise presents very great advantages which will 

 end by being appreciated. Here is an example : In the garden 

 attached to the mansion house of Biebrich, in 1892, phosphate and' 

 nitrate of potash was applied to the raspberry plantations so as to 

 obtain a heavier and an earlier yield. The success was such that- 

 the gardener of the mansion house had already sold £15 worth 



