December, '16] DUTCHER: FROZEN LEAD ARSENATES 563 



just as good with the frozen lead as with the same brand of lead before freezing, the 

 only objection being the slight extra work needed in getting the paste properly 

 mixed with water. 



The research department for a commercial house also supported 

 this view as shown in the following letter: 



We have found that if the frozen arsenate of lead is allowed to stand in a warm 

 enough place so that it can thaw out, there is apparently no difference in the form of 

 paste arsenate lead. It is barely possible that the physical condition of this frozen 

 lead when thawed is not quite as smooth as when originally made, but this is very 

 hard to state authentically as the difference is so awfully small. We have had a 

 considerable number of samples of arsenate lead analyzed after they have been 

 frozen and thawed out and there is no indication whatever that the soluble arsenic 

 has increased from the original amount that was in it when manufactured. As the 

 soluble arsenic is the biggest indication as to the changes that might take place, we 

 think we are perfectly safe in stating that no chemical change has taken place. 



Another manufacturer says: ' 



Our investigations indicate that the chemical properties of arsenate of lead are not 

 affected in any way by freezing, but the physical properties are to the extent that it 

 usually causes moisture separation, and it sometimes causes the material to become 

 granular and coarse and because of this there may be trouble by clogging the nozzles. 

 However, if this frozen material can be worked up into a good, smooth paste, and it 

 can be if the grower is willing to go to the trouble to do so by the slow addition of 

 water and using a good paddle, it will be in entirely good condition to use. 



In opposition to this view Mr. L. Haseman of the Missouri Station 

 writes : , 



This I do know — if arsenate of lead paste is permitted to freeze, it tends to form a 

 coarser preparation and more difficulty is encountered in keeping it in suspension. 



\V. J. Schoene of the Virginia Station contends that: 



The general impression is, however, that once paste lead arsenate has become 

 thoroughly dry it no longer has any value. 



The manager for one of the houses manufacturing a paste used in 

 large quantities on the Pacific Coast is quite emphatic in showing the 

 harmful effects of freezing the arsenate pastes. He writes in part as 

 follows : 



With reference to your inquiry regarding arsenate of lead in the paste form after 

 it has been frozen, would like to say that so far as I know, the pubhcations and state- 

 ments of the manufacturers are not based on experimental data, but are based on a 

 knowledge of how these things act when compressed and on actual experience. 

 For instance, most manufacturers have had at some time, experience on frozen arsen- 

 ates of lead and after thawing them out, they have found that the paste itself gives 

 up a great deal of its original water and that it was impossible to put this arsenate of 

 lead back into its original form, as denoted by such tests as the difference of the sus- 

 pension in water, adhesive properties, etc. Freezing has a tendency to granulate the 



