CHAPTER V. 



57 



enhancing their penetrating power ; 70 per cent, is a good grade for 

 this purpose. 



Table for diluting alcohol (after GAY-LUSSAC). To use this table, find 

 in the upper horizontal row of figures the percentage of the alcohol that 

 it is desired to dilute, and in the vertical row to the left the percentage 

 of the alcohol it is desired to arrive at. Then follow out the vertical 

 and horizontal rows headed respectively by these figures, and the figure 

 printed at the point of intersection of the two rows will show how many 

 volumes of water must be taken to reduce one hundred volumes of the 

 original alcohol to the required grade. 



Alcohol is an easily oxidisable substance. Chromic acid, for 

 instance, easily oxidises it, first into aldehyde, and then into acetic 

 acid. It follows that alcohol should not be combined in mixtures 

 with oxidising agents of notable energy. Further, alcohol is a 

 reducing agent, and therefore should not be combined with easily 

 reducible substances. These remarks particularly apply to chromic 

 acid. See 38, 39, 48. 



For fixing, alcohol is a very third-class reagent, only to be used 

 alone where better ones cannot be conveniently employed, though 

 it enters as a useful ingredient into many mixtures, in which it serves 

 to enhance the power of penetration. For hardening it is an im- 



