MAGNESIUM SULPHATE (EPSOM SALTS). 



161 



TABLE XX. — SJtoiving the Effect of 30 percent and 15 pe7- cent Solutions of 

 Magnesium Chloride on Plants (Steglich). 



Hitchcock and Carleton tried the action of magnesium chloride on 

 rust of cereals. They found that a 1 per cent solution prevented the 

 germination of the uredospores of Piiccinia coronata, Corda, after 

 steeping for twenty-seven hours. 



Use. — In strong doses magnesium chloride may be used to replace 

 green vitriol to destroy charlock in cereal crops ; it may act at the 

 same time as a manure. Trials made up to now with a 20 per cent 

 solution, at the rate of 35 gallons per acre, have given good results. 

 As a manure, it is recommended in pine nurseries to cure the yellow 

 leaves of the pines which show a deficiency of magnesia in the soil. 



52. Magnesium Sulphate, MgSO^TH.p. — Preparation. — By 

 evaporating the waters of certain springs such as Epsom ^ in England,, 

 and Seidlitz in Bohemia. But it is obtained more readily by attacking 

 dolomite by hot dilute sulphuric acid ; a mixture of insoluble sulphate- 

 of lime is formed and soluble sulphate of magnesia which is separated 

 by filtration. 



Properties. — Magnesium sulphate crystalli2,es with 7 molecules 

 of water- ; 100 parts of water dissolve 26 parts of calcined magnesium 

 sulphate at a temperature of 0'^ C. and 72 parts at 100" C. It possesses 

 a bitter taste and is generally used in medicine, in which it is ad- 

 ministered as a purgative. In the vegetable economy it plays the role 

 of magnesium chloride, that is to say, dissolved in small amount in 

 distilled water it is capable of prolonging the growth of plants ; when 

 the plant is strengthened it becomes indispensable to it. In 1853 the 

 experiments of J. Pierre in the plain of Caen showed that magnesium 

 sulphate could render the same service as plaster in agriculture. 



Use. — This product may be used to combat charlock in grain crops. 

 in the same waj^ as magnesium chloride. Magnesium sulphate was. 

 recommended in 1852 to combat an insect injurious to beets termed — ■ . 



A tomaria linearis, Steph. — Kuhn recommends to combat this insect, 

 to immerse the beet-seed before sowing for twenty minutes in a steep 



1 Hence the trade name of Epsom Salts. — Tii. 



- It is an efflorescent salt, i.e. loses most of its water of crystallization in 

 open atmosphere. — Tr. 



11 



dry. 



