POTASSIUM CHLORIDE (MURIATE OF POTASH). 117 



Tingis Piri, Fl. (Tigre du Poirier). — Montillot recommends two or 

 three coats with the brush in winter, at intervals of a fortnight, on the 

 branches and trunks of pear-trees with a preparation made thus : 2 lb. of 

 potassium monosulphide is dissolved in the requisite amount of water ; it 

 is withdrawn from the fire and 2 lb. of flowers of sulphur gradually added. 



Plant Lice. — Moss recommends a mixture of soap and liver of 

 sulphur, known in England as Chiswick compound, against lice in 

 general. Thumen regards 2^ per cent solutions of potassium sulphide 

 as good. The phylloxera is absolutely refractory to the action of 

 potassium monosulphide. Mouillefert tried it against that parasite by 

 spreading 480 grammes per stock in a radius of 30 centimetres round 

 root-stripped vines, and sprinkling them with 10 litres of water (2"2 

 gallons). As a matter of form, the following curious process, recom- 

 mended by Ponsard, may be quoted: It consists in boring a hole with 

 a gimlet into which 2-3 grammes of potassium sulphide was introduced ; 

 the hole was then closed with mastic. The author of this process hoped 

 that the sulphide entrained by the jus would induce the death of the 

 phylloxera, but this treatment has only given a negative result. 



Phyto-ptides. — The acari, which by irritation of the tissues of the 

 plant produce degeneration of the latter, become manifest by felt-like 

 growths known as erinoses or by peculiar swellings of bright-coloui-ed 

 tints as is seen on the pear when it has the Cloque (brown rust), may 

 be destroyed by the sulphides. Emulsions containing 3-4 per cent 

 of sulphur must be used at the moment when the acari have not yet 

 . produced the excrescences which protect them so efficaciously. Smith 

 and Williamson advise to treat chiefly the Eriojjhyes Piri, Pgst., Phy- 

 toptus Piri, by two sprayings, one before the opening of the buds, and 

 the second after collecting the fruit, or even spraying with a concen- 

 trated emulsion in winter followed by a weaker one after plants have 

 come into leaf. 



32. Potassium Chloride (Muriate of Potash), KCl ; Potassium 

 Sulphate, KoSO^.— Natural Occurrence. — Potassium chloride is 

 found (500 grammes per cubic metre) in sea-water. Potassium 

 chloride and sulphate of potash form vast underground deposits at 

 Stassfurth in Prussia and at Kalusy in Galicia. In these mines the 

 different salt beds have a different composition. Below vast deposits 

 of rock salt deposits rich in sulphate of potash are found under the 

 form of triple sulphate of lime, magnesia and potash (Polyhalite), 

 then sulphate of magnesia and potash {Kainite), and finally double 

 chlorides such as Carnallite. Carnallite, for example, contains 16 

 per cent of potassium chloride, 20 per cent of magnesium chloride, 

 25 per cent of sodium chloride, 10 per cent of magnesium sulphate, 

 and 29 per cent of impurities. For agricultural purposes these salts 

 are generally used in the impure state as brought from the mine. If 

 it be desired to purify them and to obtain pure potassium chloride, the 

 saline mass is pulverized and dissolved in large cast-iron steam-heated 

 vessels. The solution is allowed to deposit, then decanted, and left to 

 crystallize ; the potassium chloride crystallizes, entraining with it a 

 little magnesium and sodium chlorides which are removed by washing 

 with cold water. If potassium chloride be treated with sulphuric acid, 



