5-^ -MAINE AGRICULTURAL EXPERIMENT STATION. I915. 



Paris green is adulterated if it does not contain at least 50- 

 per cent of arsenic oxide ; contains more than 3.5 per cent of 

 arsenious oxide soluble in water ; or any substance has been 

 mixed or packed with it so as to reduce or lower or injuriously 

 affect its quality or strength. 



The injurious effect to foliage resulting from the use of Paris 

 green is due not to the arsenic that is in combination with the 

 copper but the free Avater soluble arsenic. Under the statute 

 a ver}' liberal amount, equivalent to 3.5 per cent of arsenious 

 oxide, or 2.65 per cent arsenic is permitted in the case of water 

 soluble Paris green. Several samples of Paris green were ex- 

 amined previous to 1913 and like all of the other greens which 

 we have examined they carried more arsenious oxide than could 

 be combined with the copper present. That is, the total amount 

 of arsenic exceeded in every instance the minimum required 

 under the law. This follows, as pointed out in earlier publica- 

 tions from the fact that white arsenic is the cheapest ingredient 

 that goes into the makeup of Paris green, and hence the manu- 

 facturers will always use as much of it as possible and still have 

 a green of good color. It is gratifying to note the marked 

 improvement in the quality of Paris green in respect to its water 

 soluble arsenic. 



It will be noted that two of the samples examined (see table 

 on page 33) were short weight. One sample contained more 

 water soluble arsenic than claimed, and one contained more 

 water soluble arsenic than is allowed under the law. 



Water soluble poisons, consisting practically of sodium arse- 

 nate, are prepared for the purpose of being used on potatoes to 

 fight potato bugs in connection with bordeaux mixture. The 

 three brands registered in 1914 were found to be in accordance 

 with their claimed composition. The tabular results are given 

 on page 33. 



Fungicides and Insecticides Containing Both Copper and 

 Arsenic. There are a number of brands, consisting of copper 

 in- combination more or less analogous to that in bordeaux mix- 

 ture to which has been added some poison, usually Paris green 

 or lead arsenate, which are registered within the State. These 

 are convenient preparations for the small grower, although if 

 used in accordance with directions they are not as effective in 

 preventing blight as regular bordeaux mixtures. They are 



