LONDON PURPLE. 233 



whereas we have no doubt that very serious consequences have followed 

 the use of an adulterated article. 



We have endeavored to find some simple method by which any planter 

 could test for himself the purity of Paris-green. The following, although 

 it does not meet all requirements, will be found useful. Pure Paris 

 green is soluble in ammonia; hence, if you take 100 grains of Paris 

 green and place it in a glass vessel and add one ounce of liquid ammonia 

 (it may require more than one ounce if the ammonia be not strong), 

 and stir it for a minute or two with a glass or wooden rod, the Paris 

 green will completly dissolve, forming a beautiful blue transparent solu- 

 tion. Should there be sediment it will indicate that the Paris green is 

 adulterated ; and the amount of sediment will show the amount of adul- 

 teration. This test will serve to detect the presence of any of the 

 substances ordinarily used for adulteration of this poison. Sometimes, 

 however, white arsenic is used for this purpose, and as this substance is 

 also soluble in ammonia its presence cannot be detected in this way. 

 By using the above test, however, the planter can be certain that the 

 compound in question will be efficient as an insecticide. There remains 

 only the danger of his cotton being injured by the caustic action of 

 adulterating arsenic. The best plan is to buy the poison directly of the 

 manufacturer. In this case, if care is taken to deal only with reliable 

 firms, little danger need be apprehended. 



It is proper to state that although our experiments with the Texas 

 Cotton-Worm Destroyer as well as those conducted by some of our cor- 

 respondents in Alabama failed to produce satisfactory results ; many 

 strong recommendations of this remedy have been received from west- 

 ern portions of the cotton belt, especially Texas ; and in the circular 

 published by Preston and Robira are recommendations from many 

 prominent planters. An analysis shows that this remedy is an arseni- 

 ate of sodium, which is almost entirely soluble in water. Of course its 

 value as an insecticide is due to the arsenic which it contains ; its only 

 advantage over other compounds of arsenic is its solubility in water, 

 and we are inclined to believe that this advantage is more than counter- 

 balanced by the fact that there is greater danger of injury to the plant 

 from a solution of this kind than by a mere mechanical mixture with 

 water. This point is illustrated by an experiment tried with Fowler's 

 solution. 



As to the results of the experiments with London purple, we are dis- 

 appointed. We had hoped, owing to the cheapness with which it can 

 be furnished, that it would prove a substitute for Paris green, but our 

 experience indicates that it is even less desirable than commercial arse- 

 nic. We hesitate, however, to give a decided opinion with only the re- 

 sults of a single season's trial before us, especially as we have favorable 

 reports from Prof. C. C. Bessey, of the Iowa State Agricultural College, 

 who has experimented with it as a remedy for the potato beetle, and 

 from Mr. A. K. Whitney, of Franklin Grove, 111., who has successfully 



