THE VENETIAN TURPENTINE METHOD 
103 
5. Stain over night, or 24 hours, in \ per cent aqueous solution haema- 
toxylin. 
6. Wash in water, 20 minutes. 
7. 2 per cent aqueous solution of iron-alum, until the stain is satis¬ 
factory. This can be determined only by examining frequently 
under the microscope. 
8. Wash in water, 2 hours. If this washing is not thorough, the con¬ 
tinued action of the iron-alum will cause the preparations to fade. 
9. Transfer to 10 per cent glycerin, and allow the glycerin to concentrate 
until it has the consistency of pure glycerin. It is not necessary to 
use an exsiccator. Merely put the glycerin into shallow dishes, and 
leave it exposed to the air, but protected from dust. If the material 
is in Petri dishes or other dishes with a large surface, 3 or 4 days 
will be sufficient. This process may be hastened by warming, if 
the temperature does not go above 35° C. If the reduction from 
10 per cent glycerin to pure glycerin is accomplished in less than 
24 hours, the change in the concentration is so rapid that material is 
likely to suffer. 
10. Wash out the glycerin with 95 per cent alcohol. It will be necessary 
to change the alcohol several times. From 10 to 20 minutes will be 
sufficient if the alcohol is changed frequently. This alcohol cannot 
be used again for the same purpose, but it will be useful in cleaning 
one’s hands and in cleaning dishes which have contained Venetian 
turpentine. 
11. Complete the dehydration in 100 per cent alcohol: 10 minutes should 
be sufficient. 
12. Most failures are now ready to occur. 
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 effective 
exsiccator. Instead, you may simply scatter soda lime in the bottom 
