32 



Paris Green. This is too commou a substance to need desci'iption 

 and is used in preference to London purple because it is more uniform 

 in composition and results than the latter. 



Many cases of injury to the foliage have been reported from the 

 use of Pans green and as far as now determined this injury is in 

 proportion to the amount of soluble arsenic or arsenious acid con- 

 tained in the sample used. Several samples of pure Paris green 

 obtained from reliable manufacturers, as analysed at the station 

 laboratory, show the following composition : 



Samples. No. 1. No. -2. No. 3. 



Moisture 1.38 1.05 .67 



Arsenious acid 54. So 54.14 53.73 



Copper oxide 32.55 31.05 30.60 



Arsenious acid soluble in cold water 4 per cent. 



" " " " boiling " 8 to 9 per cent. 



If, as we have reason to believe, the injury is in proportion to the 

 •amount of soluble arsenic in the Paris green, the injury, so often 

 reported, may be due to putting this substance into heated lime 

 mixtures, to the heat generated by the chemical action in mixing the 

 two or to the heat developed by the sun on globules of water sttinding 

 on the leaves. If therefore the above be correct Paris green should 

 never be put into liquids until thoroughly cooled. These points 

 however, will receive careful investigation and the results be reported 

 in a future bulletin. It is well known, that by adding the milk of 

 lime to the water containing Paris green or by using the latter with 

 the Bordeaux mixture, much more of this insecticide can be used 

 and little or no injury result, than if u=ied in water alone. One 

 gallon of the milk of lime to ten gallons of the water containing Paris 

 green as ordinarily used, i. e. 1 lb. to 150 or 200 gallons of water, 

 will be sufficient. 



The use of the Bordeaux mixture has become a necessity to protect 

 most of our crops from fungous pests and as the litne in this mixture 

 has the same effect as the milk of lime, we urge their combined use, 

 thus reducingthe costforthe destruction of each pestto the minimum. 



THE "new process" PARIS GREEN. 



The " new process " Paris green, as shown by the analysis of 

 several samples made by the chemical department of this station is 

 not Paris green at all, but a combination of lime and arsenious acid 

 with a small amount of copper oxide. 



This article is olTered for sale by some of the large dealers in seeds 

 and horticultural supplies in this and other states, and as many 

 reports have come to us of its having seriously injured the foliage 

 when used last summer, we would advise those intending to use this 

 material the coming season to make a very careful trial on a small 

 scale before applying it to the valuable crops. The analysis of these 

 -samples shows the following : 



