REPORT OP COMMITTEE ON PUBLICATION 167 



with a paddle or knead with the hands, breaking up all the lumps as thor- 

 oughly as practical. The stirring or kneading should be continued for three 

 or four minutes, until the sulphur is thoroughly wetted and forms a smooth 

 creamy paste. 



"Place the box (A) in position in the opening of the spray tank and run 

 into it as much as desirable of the wet sulphur; then work the sulphur 

 through the sieve with the brush, using the remainder of the glue solution 

 to help wash it through. Should more liquid be required for this purpose, 

 water taken from the spray tank may be used." 



So far as known, the only wettable sulphurs to come into use in this 

 State are a so-called "iron sulphide" and two proprietary preparations. 



Iron Sulphide: The first was devised by Ballard and Volcki as a remedy 

 against the powdery mildew of the apple. The fungicide is prepared by mix- 

 ing a solution of iron sulphate with an excess of lime-sulphur solution. There 

 results a mixed precipitate of insoluble iron sulphide (black), free sulphur 

 (yellowish), and calcium sulphate (white). The excess of lime-sulphur is 

 washed out and there is left a paste of the three precipitates which are quite 

 insoluble and inert toward most ordinary reagents. The iron sulphide is 

 black and is present in sufficient quantity to mask the presence of the other 

 precipitates. The precipitated sulphur is believed to be the only constituent 

 of fungicidal value, the others being merely incidental to this economical 

 manner of precipitating free sulphur in a finely divided form. The iron 

 sulphide and calcium sulphate also serve to prevent the minute particles of 

 sulphur from flocculating (i. e., uniting to form coarser grains). 



The directions for the preparation of sufficient stock to make five hun- 

 dred gallons of spray are as follows. 



"Fill a 50-gallon barrel about two-thirds full of water. Weigh out 10 

 pounds of iron sulphate (copperas), place in a sack, and suspend in the water. 

 The iron sulphate will dissolve fairly rapidly, and when it is all in solution 

 measure out carefully 2~y gallons of commercial lime-sulphur solution test- 

 ing 33 Baume, or 2 gallons and 3 pints of a lime-sulphur solution testing 

 32 Baum6. Slowly pour all but 2 pints of the lime-sulphur solution into the 

 iron-sulphate solution in the barrel, stirring the mixture vigorously with a hoe 

 or shovel. The addition of the lime-sulphur solution will produce a bulky, 

 black precipitate, and when all but 2 pints of the lime-sulphur solution has 

 been added the mixture should be allowed to stand for a few minutes, when 

 the black precipitate will begin to settle and a little of the clear liquid at 

 the top can be carefully dipped out with a clean glass or cup. This clear 

 liquid will probably show no yellow lime-sulphur color, which means that an 

 excess of lime-sulphur solution has not yet been added. In other words, 

 there is still some iron sulphate in solution, in which case the addition of a 

 drop of lime-sulphur solution to the clear liquid in the glass will produce a 

 black precipitate. This means that more lime-sulphur solution should be 

 added to the stock in the barrel, and about half of the remaining 2 pints should 

 now be poured in and the contents of the barrel stirred vigorously and 

 allowed to stand. Some of the clear liquid should again be dipped off and 

 tested as before, to determine whether an excess of lime-sulphur solution has 

 been added. If necessary, the addition of small quantities of lime-sulphur 

 solution should be continued until some of the clear liquid dipped from the 

 top, after the contents of the barrel have been well stirred and allowed to 

 settle, shows a pale yellowish lime-sulphur tint. The purpose of using a slight 

 excess of the lime-sulphur solution is to insure all the iron sulphate being 

 utilized. The voluminous black precipitate that is formed consists of iron 



i Ballard, W. S., and Volck, W. H., "Apple Powdery Mildew and Its Con- 

 trol in the Pajaro Valley/' U. S. D. A. Bui. 120 (1914). 



