Station Laboratory will clieerfuU}' test any samples for- 

 warded for examination by planters from any section of the 

 State. 



Any fraudulent goods of this character can thus be readily 

 driven from the market, and the planter can then be assured 

 as to the absolute purity of the insecticides which he may 

 purchase. 



METHOD OF ANALYSIS. 



The following is the process adopted in the Laboratory 

 for the determination of arsenious acid in Paris Green : 



Weigh one gram of the material, and place in a medium 

 size beaker or flask ; add about 30 cubic centimetres of 

 strong hydrochloric acid and digest on a water bath, at a 

 temperature somewhat below the boiling point, adding at 

 frequent intervals, small quantities of finely powdered po- 

 tassium chlorate. Continue the heating until the odor of 

 free chlorine has almost disappeared ; dilute with water, 

 and filter, if necessary. Add ammonia in slight excess, cool 

 and add magnesia mixture gradually, stirring vigorously all 

 the while. Allow to stand 12 hours, filter and wash pre- 

 cipitate with ammonia water. 



Dry filter and contents : detach precipitate from filter as 

 completely as possible ; ignite filter, using ammonium ni- 

 trate solution to facilitate ignition. Transfer the precipitate 

 to a porcelain crucible, and heat for a while on an iron 

 plate, and finally with the direct flame. Add filter ash to 

 the precipitate and Aveigh as magnesium pyro-arsenate. 



(Note. — Of course, this method is only applicable in the 

 absence of phosphates and arsenates.) 



