No. 7. DEPARTMENT OF AGRICULTURE. 655 



Along in 1908, when the writer became interested in the situa- 

 tion, the making of these dense, non-crystalizing insecticides was 

 supposed to be accomplished by some difficult, factory process, wholly 

 beyond the capabilities of the orchardist, and consequently worth 

 about three times as much to him as we now know they can be readily 

 made for at home. 



At this time it was learned that Cordley in Oregon had made 

 a "stock solution" lime-sulphur. Details of his work were meager, 

 however, and not generally available. There also appeared to be 

 some doubt as to the correct ratio of lime to sulphur, and the proper 

 concentration to be used. For example in the version of his formula 

 given by ran of!, 60-to-125 ratio was advised, while in his own 

 later accoimt, GO-to-llO was used; the latter ratio having appeared 

 in 1906 in a formula used by Thatcher, at one-half the present 

 weights. As to concentration used, it appears that with the large 

 amounts of ingredients only enough water was added at first to 

 make 45 gallons of mixture, while with the smaller amounts the total 

 was brought up to 60 gallons. No further additions of water were 

 indicated in either account to make up for the losses in boiling, 

 which was to be for one hour or more. After boiling and settling, 

 only the clear liquid obtainable above the sediment was drawn off; 

 and in the former case this amount of liquid was diluted to make 

 the final 50 gallons of concentrate. This was again diluted for use, 

 at the rate of 1 to 10 (total), and the sediment was to be re-used 

 in succeeding boilings. 



The faults and uncertainties of this method are very evident 

 now; and it was doubtless fortunate for the home-made concentrate 

 that no wide attempt was made to strictly carry it out in orchard 

 practice. It is of interest, however, as marking the advance made 

 up to the early part of 1909. 



The next move was made at the Pennsylvania Station. The work 

 had begun before the above accounts appeared, though most of their 

 facts were known. The general attitude and prospects for success 

 at that time may be gathered from a remark by one of our leading 

 insecticidal chemists, then at the Station, whom the writer was 

 trying to enlist in the cause. His advice was to go ahead with 

 the work but not to be disappointed in case nothing was learned, 

 because the whole subject had been studied thoroughly already by 

 chemists, and nothing new was to be expected. 



The results of the subsequent work have appeared in various 

 places, and we can here merely mention some of the leading points 

 established. We found that the crystals occurring in the old, dilute 

 preparation were due to excess of lime. The value of this excess 

 was questioned and later proved to be unnecessary against scale, 

 as was already known in the case of fungi. The cause of the crust 

 wiiich develops over concentrates was shown to be due to exposure 

 to air, and its prevention was readily accomplished. 



The proper ratio of lime to sulphur was studied, and the ratio 

 of these materials in solution was found not to be constant as 

 Thatcher supposed (Wash. Bui. 76) but to vary primarily with 

 increase in density. Thus in dilute solutions the ratio occasionally 

 ran as low as 1 to 1.8 while in dense concentrates it averaged about 

 1 to 25, with individual cases much higher. Owing to losses in 



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