SODIUM SULPHATE. 103 



By adding 300 grammes of hyposulphite of soda to a 1'5 per cent 

 bouiUie boi'delaise. Kaserer obtained by three sprayings in a year 

 complete success in treating oidium without the treatment being 

 followed by the burning of the leaves. Solutions of hyposulphite 

 to which milk of lime was added have been found more energetic than 

 sulphur. 



Sphcerotheca pannosa (mildew of the rose). — Vesque proposes 

 hyposulphite of soda to destroy mildew of the rose. 



Giugnardia Bidwelli, Viala et Ravay (black rot of vine). — Pauly 

 remarks that the double salt, hyposulphite of soda and silver, is 

 capable of arresting the progress of the black rot in full evolution ; 

 used in a 1 per cent solution its effect on the spores and the mycelium 

 is most conclusive. This product has therefore been used to destroj 

 this disease by making three sprayings per annum on the attacked 

 vines. This treatment, which burned the leaves, has not been the 

 success anticipated. 



Crouzel's anticryptogamic which contains both calcium poly- 

 sulphide and a little naphthaline, and 0"2 per cent of hyposulphite of 

 soda is recommended to combat the cryptogamic diseases of the vine, 

 and particularly the black rot and the oidium. Spraying should 

 alternate with five or six days' interval with those made from copper 

 preparations. 



Dematophora necatrix, Hartig (white root rot). — Dufour used this 

 salt without appreciable result. 



24. Sodium Sulphate, Na.^S04. — Occurrence. — In Spain vast 

 mines of sodium sulphate have been exploited for some years. 



Preparation. — By decomposing sodium chloride by sulphuric 

 acid : — 



2NaCl + HoSO, = Na.SO, + 2HC1. 



Properties. — Crystallized sodium sulphate or Glauber's salt con- 

 tains 10 molecules of water of crystallization. Heated, these crystals 

 melt in their water of crystallization and lose it by igneous fusion. 

 Anhydrous sodium sulphate, a white amorphous powder, is formed. 

 Sodium sulphate reaches its maximum solubility in water at 33° G. 

 It is a neutral body which has no action on plants except when highly 

 concentrated. Seeds, however, do not stand without injury prolonged 

 immersion in a bath of 2 per cent of sulphate of soda. 



Use. — Mathieu de Dombasle discovered the injurious action of 

 this salt on the spores of smut and b2t7it, and proposed it 

 to replace common salt then in use to disinfect grain by sodium 

 sulphate. The process in use up to then had many drawbacks. It 

 consisted in macerating the grain in a mixture of lime and common 

 salt for twenty-four hours, and only gave incomplete results. The 

 use of the " Absolute Preservative of Mathieu de Dombasle " was a 

 real progress from all points of view ; it shortened the long immersion 

 and gave a better result without injuring the grain treated. Process. — 

 Dissolve 8 kilogrammes (17-6 lb.) of sodium sulphate in 100 litres (22 

 gallons) of water. Spread on the water-tight floor (of a ground floor) 

 1 hectolitre (2| bushels) of the grain to be disinfected and wate: the 



