218 Infestation of Fungus Cultures by Mites 



impurity commercial Pyridine would prove deleterious to fungi and so 

 inhibit its use or render its fractionation and purification indispensable. 

 Moreover, it was important to ascertain whether the actual toxic product 

 in the commercial article was Pyridine itself or some impurity. 



For purposes of reference and comparison the specific gravity and the 

 fractions distilhng at various temperatures were determined. 



The distillations were carried out in the following way: 



75 c.c. were distilled at a rate of one drop per second from a 150 c.c. 

 flask (neck 9 cm. long, diameter of bulb 6-5 cm.) fitted with a four-pear 

 fractionating column of a length from bottom to side tube of 24-5 cm. 



The column was so adjusted into the neck of the flask that the total 

 length of still-head was just about 30 cm. A Davies double jacketed con- 

 denser in a perpendicular position was attached to the side tube of the 

 column. The distillates were collected and measured. The results are 

 tabulated in Table III. 



Table III. 



Fractional Distillation of Three Samples of Pyridine. 

 75 c.c. distilled at a rate of 1 drop per second. 



An inspection of this table shows that there are wide dift'erences in 

 the composition of the three samples, that the commercial product 

 (which contains about 34 per cent, water) has a considerable fraction 

 distilling off between 95° and 100° C, and that the sample labelled Pure 

 is misrepresented. The last point was confirmed by testing with Per- 

 manganate which was rapidly decolourised. In view of the obvious 

 impurity of the Pyridine labelled "Pure," this sample was treated with 

 Potassium Permanganate, dried over solid Caustic Potash and frac- 



