2IO THE CONNECTICUT POMOLOGICAL SOCIETY. 



In this connection, attention has been called to the 

 fact that the "Federal Insecticide Act of 1910,'' by requir- 

 ing a minimum of 12^% arsenic oxid, rules out the com- 

 mercial preparation of neutral lead ortho-arsenate on a 50%- 

 water basis. The manufacturers may still comply with this 

 law, however, by reducing the water. The latter reduction 

 seems entirely practicable, judging from the increasing use 

 of the powdered forms of lead arsenate, in which the water 

 has been eliminated almost entirely. 



The Ammonia Te.st for Lead Ortho-arsenate. 



If one wishes to use the ortho-arsenate, as appears 

 desirable from our field tests noted above, it is highly im- 

 portant that he should know when he has it. Already the 

 term acid arsenates — which refers especially to the 

 PbHAs04 and the PboAs207 compounds contained as a 

 mixture in most if not all of our Eastern lead arsenates — 

 has been interpreted commercially to mean an acid reaction 

 in the ordinary lead arsenate paste. Hence a litmus test 

 is being offered to show that such a reaction does not exist 

 in certain materials, and therefore they are considered to 

 be neutral and free of the undesirable forms. Other lead 

 arsenates are being oft'ered as neutral and containing 12^% 

 arsenic oxid. 



None of these tests or descriptions is sufficient to 

 make certain that a given material contains nothing but a 

 strictly neutral ortho-arsenate of lead, Pbs (As04)2. At 

 present this latter fact can be determined only by the so- 

 called "ammonia test" or by a reliable guarantee that con- 

 tains no substitution nor modification of terms. 



The ammonia test is based essentially on the fact 

 that the acid arsenates are soluble in alkalin and not in 

 acid solutions. This test is made as follows : 



A fair sample (10 to 20 grams) is mixed with water 

 (25 to 50 cc.) and an equal volume of strong ammonia 

 (26° Be.) is added. This is heated gently, agitated and 



