154 



Dm = .Me/kT, Dp = Pe/kT', Dm' ^ Me/k'l", Dp' = To/kT ; there- 

 tore 



n = MoT'/PeT and b ^ PeT'/MeT, 



ii/b = Me/Pe, 



Me/Pe =-- a /I I. 

 Substitutiii,2 the vahics of a and b as .i^ivcii above, Me/Pe == 2.45/1.52 

 = 1.27. 



This latio of effective concentrations confirms the hypothesis that 

 ev(,'n clear solutions of zinc chloride contain colloidal products of hydro- 

 lysis. Aluminum sulphate, through its own hydrolysis and the foruiatiou 

 of free sulphuric acid, causes a partial repression of the hydrolysis of 

 zinc chloride and in 3% zinc chloride solutions, such as are used in wood 

 presen'in.c, there is approximately 80% as much zinc present in true solu- 

 tion as is the case when 1.5% of aluminum sulphate has been added. 

 The remaining zinc is in the form of a hydrosol of basis zinc chloride 

 or of zinc hydroxide and cannot pass into the interior of treated wood 

 but must be loft in the outer layers. It is to be expected that any other 

 easily hydrolyzed salt of a strong acid would have a similar effect upon 

 the penetration of zinc salts into wood. The use of free acid itself would 

 have the same effect if it were used intelligently. 



Fui'ther experiments ai-e now in progress. 



Purdue Universiti/, 

 Ncn-emljer, 1912. 



