Reagents 



33 



the Stenders. The importance of excluding moisture cannot be 

 exaggerated. 



The lower grades are made up from 95 per cent alcohol. 



Formulae for Alcohols.- -The following formulae will enable 

 anyone to make the other grades of alcohol from 95 per cent alcohol 

 and water. 



The foregoing are the formulae for various alcohols from 10 to 

 85 per cent. The first column shows the formula for making 10 per 

 cent alcohol. The percentage of alcohol secured in each case is 

 indicated by the middle number in each column. In the first formula, 

 subtract 10 from 95; the result, 85, is the number of cubic 

 centimeters of water which must be added to 10 c.c. of 

 95 per cent alcohol in order to obtain 10 per cent alcohol. 

 The mixture contains 95 c.c. of 10 per cent alcohol. If 

 more or less than 95 c.e. of the mixture is needed, take 

 proportional parts of 10 and 85. This simple method is 

 a time-saver, but if the bottles or Slender dishes are to 

 be filled frequently, it will be a still further saving of 

 time to use a long label (Fig. 13) and, after pouring in 

 the 95 per cent alcohol, draw a line showing how high it 

 reaches, and then, after pouring in the water, draw 

 another line. The next time it is necessary to fill the 

 bottles merely pour in 95 per cent alcohol until it 

 reaches the first line, and then pour in water until it 

 reaches the second line. It is not necessary to use distilled water if 

 pure drinking-water is available. 



Synthol is used like alcohol, and many believe it to be a good 

 substitute. 



Some investigators use more or less complicated diffusion appa- 

 ratus and make the dehydration process extremely gradual. Judging 

 from the finished preparation, we find no advantage in the method. 

 In the diffusion process, the solution is constantly changing. This 

 may not be an advantage. 



70 



per cent 



FIG. 13.- 

 Label for 

 staining-dish. 



