INJURIOUS INSECTS OF 1903. 



35 



(a) The Microscope Test: A very little of the sample 

 is taken on a knife blade, deposited on a glass slide and the 

 slide inclined and tapped, until the green is spread out in a 

 long, thin sheet. The color of this thin sheet should be bright 

 green ; if pale green or white to the naked eye it is undoubtedly 

 adulterated, certainly so if it is white. This is then placed 

 under the microscope. If the Paris Green is of good quality it 

 will look like Fig. 13, in which the round grains of the 

 pure article can be seen unmixed with any adulterating mate- 

 rial. If adulterated,, the adulteration appears under the micro- 

 scope as many small granules amongst the large more or less 

 spherical grains of Paris Green. 



(b) The Ammonia Test: Consists in adding Paris Green 

 to ammonia. We used 25 cc of ammonia (one wine glassful), 

 and added one gram of Paris Green (about one-fourth tea- 

 spoonful). The ammonia turns blue. If, upon thorough stir- 

 ring, sediment settles in the bottom of the glass, one may rest 

 assured that the sample is adulterated. Silica, calcic carbon- 



Fig. ii. Fig. 12. 



Fig. 11. — Ammonia in wliich all tlie "Paris Green" was dissolved. 

 Fig. 12. — Sample showing insoluble adulterations. 



ate, barium sulphate and sodium sulphate, sometimes used to 

 adulterate Paris Green, are insoluble in ammonia. It must be 

 borne in mind, however, that some adulterants of Paris Green, notably 

 arsenic, are frequently soluble in ammonia, hence this is but a negative 

 test. A very good rule to follow would be to avoid using any 

 Paris Green which was not completely soluble in the above test. 



