154 



Dm = Me/kT, Dp = Pe/kT', Dm' :^ Me/kT', Dp' = Pe/kT ; there- 

 tore 



a = MeT'/PeT and b = PeT'/MeT, 



a/b = Me/ Pe, 



Me/Pe =- a/b. 

 Substitiitiiiii' the values ul' a and b as L'ivcn above, Me/Pe = 2.45/1.52 

 =- 1.27. 



This ratio of effective concentrations confirms tlie Iiyi)otliesis that 

 even clear solutions of zinc chloride contain colloidal products of hydro- 

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

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

 zinc chloride and in ?>% ziiic chlorid(> solutions, such as are used in wood 

 ]iresen'ing, there is approximately 80% as much zinc present in ti*ue solu- 

 tion as is the ease 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 left in the outer layers. It is to be expected that any other 

 easily hydrolyzed salt <if 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 eflect if it were used intelligently. 



Furthei- experiments are now in progress. 



I'Kidiic I'niicrsHif, 

 Norriiihcr, 1012. 



