POTASSIUM NITRATE. 121 



nitrate. The growth of the conidia of PlmjtojMlwra infestans, De By., 

 is not stopped by an 1 per cent solution, but the formation of zoo- 

 spores is prevented. The growth of the conidia is not hindered until 

 a 1 per cent solution is used. The zoospores are at once killed by 

 this solution. The spores of Peronospora Viticola, De By., are a little 

 more sensitive. A O'Ol per cent solution hinders their growth a 

 little ; with a 0-1 per cent solution the conidia cannot form zoospores. 

 Their motion is slackened, and after fifteen hours none reach their 

 normal growth ; a 40*4 per cent solution interferes with the growth 

 of Ustilagq Carbo (smut), a 50-5 per cent solution stops it. A 50-5 per 

 cent solution lowers the vitality of the spores of Puccinia graminis, 

 Pers., but they are only killed with a 101-1 per cent solution. A 101 

 per cent solution does not destroy the vitality of the spores of Claviceps 

 j)urpurea (ergot), Tul. Nitrate of potash therefore, even in strong 

 doses, is deficient in real anti-cryptogamic properties. It has no toxic 

 action, but merely exerts an unfavourable effect on the development 

 of the spores by producing plasmolysis. Like many substances, 

 potassium nitrate acts as an astringent when it is used in concen- 

 trated solution. As such it may prevent all cryptogamic evolution, 

 but that is all its effect. If the spores, the growth of which has been 

 momentarily suspended, are washed and I'eplaced in good conditions, 

 they generally develop normally. 



Use. — Nematus Eibesii, Scop, (gooseberry and currant saw-fly) ; 

 Abraxas gross idar lata, L. (the magpie moth). — Taschenberg uses 

 against these two gooseberry pests a spray of a 1-2 per cent solution 

 of nitrate of potash. 



34. Carbonate of Potash, K.COg.— Preparation.— The impure 

 commercial potash is obtained by incinerating terrestrial plants. This 

 incineration is done where there are many forests and where the 

 means of transporting wood are difficult. The ashes obtained, which 

 do not contain more than 5-20 per cent of carbonate of potash, 

 are washed in casks and are exhausted after three or four washings. 

 The collected liquors are evaporated and yield the salt which calcined 

 in contact with air furnishes commercial potash, consisting mostly of 

 carbonate of potash with a small amount of potassium sulphate and 

 chloride. ^ 



Properties. — Dehquescent. Dissolves in its own weight of water. 

 Eeaction strongly alkaline. 



Action of Carbonate of Potash on Plants. — Used in agriculture 

 carbonate of potash by its alkalinity plays the role of lime, i.e. it 

 corrects the acidity of the soil and utilizes the nitric ferments which 

 can only work in a slightly alkaline soil. The nitric acid so formed 

 increases the crop. Carbonate of potash can thus greatly alter the 

 flora of an acid meadow. The reeds and rushes of the acid land dis- 

 appear to the benefit of the useful gramineae and leguminosae. This 



1 Ti-a7islator's Note. — Fabulous amounts of potash are produced in Eussia by 

 the incineration of sunflower stalks, and a big trade is done both with London and 

 New Yoi'k in such potash. But as Fritsch well points out, to grow any plant as a. 

 source of potash would be to go round in a vicious circle (see Fritsch's " Chemical 

 Manures," Scott, Greenwood & Son, which gives a detailed description of all German 

 potash mineral salts). 



