Manchester Memoirs, Vol. Ixv. (1921), No. 12 7 



three dimensional scale model, marking the viscosity, heat of 

 dilution, and boiling- points of the solutions on the three axes. 

 It will be noticed on examining the curves given in Fig. 2 

 that whereas potassium-manganese thiocyanate is well out of 

 the solvent area owing to its negative heat of dilution, the 

 corresponding sodium double salt enters the area. Experi- 

 mentally all efforts to dissolve cellulose in the potassium- 

 manganese thiocyanate solution of any concentration have 

 failed, but it readily dissolves in the solution of the sodium 

 salt boiling at 134 C. 



(80 



1*0 



&o\.L\ng 

 (60 



150 



1*0 



140 



110 



SouUTlON Aftfc* 



A . 5>oliu.mT)aoc<j*Tiahe 



Viscosity 



C- Sodium *Zvne~DuocjA7ia.te. 



6 i» TDctcutic 



E " Cd<3"mvu.m 



8 



I ig. 3. 



This difference between the sodium and potassium thio- 

 cyanates and their double salts is very clearly shown in Fig. 2. 

 The negative heat of dilution of the potassium thiocyanate 

 solution becomes larger and larger as the concentration 

 increases, but with the solution of the sodium salt it becomes 

 less and less negative, and finally positive. 



The solution of the sodium thiocyanate fails to become a 

 cellulose solvent because of its low viscosity, and likewise the 

 potassium salt for the same reason, and also on account of its 

 negative heat of dilution. 



