The Venetian Turpentine Method 99 



From the absolute alcohol the material is transferred to a 10 

 per cent solution of Venetian turpentine in absolute alcohol. The 

 turpentine thickens as the alcohol evaporates, and when it reaches the 

 consistency of pure glycerin the material is ready for mounting. 

 The 10 per cent Venetian turpentine is very sensitive to moisture, and 

 most failures are due to this characteristic; consequently the con- 

 centration cannot be allowed to take place with the turpentine 

 exposed to the air of the room. Use an exsiccator. This will not 

 only absorb the moisture from the air, but will soon remove the 

 alcohol from the turpentine mixture. Make an exsiccator as follows: 

 Place a saucer full of soda lime (sodium hydroxide with lime) on a 

 plate of glass, and cover with a bell jar. This is a simple and effect- 

 ive exsiccator. Instead, you may simply scatter soda lime in the 

 bottom of any low museum jar with tight-fitting cover. The 

 saucer of soda lime may be placed on a smooth board and covered 

 with a perfectly tight box. You may improvise other forms; the 

 essential thing is to provide a small air-tight space in which the soda 

 lime may work. 



Instead of soda lime you may use fused calcium chloride or the 

 white sticks of sodium hydroxide. 



Paint the exsiccator black, or cover it with black paper, or in 

 some other way shut out the light. Many stains are weakened 

 by light. 



We are now readv for the transfer from absolute alcohol to the 



V 



10 per cent Venetian turpentine. Make the transfer quickly. Pour 

 off the absolute alcohol and place the dish, with the material, in the 

 exsiccator; then pour on the 10 per cent turpentine, and immediately 

 put on the cover. This is better than to pour on the turpentine and 

 then try to get the dish well placed in the exsiccator. 



The greater the surface of soda lime exposed, the more rapid 

 will be the concentration of the Venetian turpentine. The con- 

 centration must not be too rapid. Not less than 2 days should be 

 allowed for the concentration of 30 c.c. of the turpentine in an 

 ordinary Minot watch glass. 



Great care must be taken not to let any of the soda lime, or other 

 drier, get into the turpentine. 



