REPORT OF COMMITTEE ON PUBLICATION 169 



and in green-houses. Recommendations have occasionally been made for 

 their use in connection with large spraying operations in vineyards to meet 

 certain unusual conditions where quick action is needed. The action of the 

 soluble sulphur fungicides is more rapid than that of sulphur or sulphur 

 pastes. While not advising their use in general practice, BiolettU recom- 

 mends liver of sulphur, alkali polysulphides, or lime-sulphur salt sprays in 

 exceptional cases where "through neglect of proper sulphuring the vines may 

 be badly attacked by mildew, and owing to the coolness of the weather when 

 the trouble is first perceived sulphur may act too slowly." 



Another soluble sulphur spray which has gained great popularity among 

 horticulturists is lime-sulphur solution. This acts both as a fungicide and an 

 insecticide. Very little success has attended its use for the control of the 

 powdery mildew of the apple in the principal apple growing section of the 

 State for the reason that it has been found impossible to apply it in suffi- 

 cient strength without fear of foliage injury. Most excellent results have 

 been obtained from its use in the control of apple scab, for which purposes 

 it is rapidly supplanting Bordeaux mixture. It has been advocated for grape 

 vines. 



Composition and Properties: The alkali sulphides represent the earliest 

 sulphur fungicides which have been used in soluble form. Caustic soda and 

 caustic potash as well as the alkali carbonates will under proper conditions 

 form a chemical compound with sulphur which is readily soluble in water. 

 The reaction between sulphur and potassium hydroxide in equeous solution 

 has been studied by Professor H. V. Tartar of the Oregon Agricultural Ex- 

 periment Station.! He concludes that "the primary reaction of sulphur with 

 potassium hydroxide in heated aqueous solutions takes place as represented 

 by the following equation: 



6KOH + 8S = 2K 2 S 3 + K 2 S 2 O 3 + 3H 2 O." 



and that "when sulphur is used in excess, a secondary reaction occurs in 

 which it combines, if present in sufficient quantity, with the trisulphide to 

 form the pentasulphide. Potassium tetrasulphide is perhaps formed as an 

 intermediate product. The variation of temperature (below 100) and con- 

 centration does not alter the nature of the reaction." This reaction may be 

 taken as typical of what occurs in the making of a similar sodium sulphide 

 or in the making of lime sulphur solution. From the results of analyses 

 made at the Insecticide Laboratory it also appears that much the same 

 products are formed when potassium or sodium carbonate is fused with sul- 

 phur. In the case where the hydroxide is used, the by-product is water, but 

 if the carbonate is used, the by-product is carbon dioxide, the final products, 

 however, being almost identical. Interpreting the chemical formula given 

 above, it is seen that the product consists of potassium polysulphide and 

 potassium thiosulphate. This reaction is very similar to the one involved in 

 the preparation of lime sulphur solution, in the latter case the principal in- 

 gredients being calcium polysulphide and calcium thiosulphate. According 

 to the best evidence at hand it is thought that in all of the above mentioned 



i Bioletti, F. T., "Oidium or Powdery Mildew of the Vine." California 

 Agr. Expt. Sta., Bui. 186, page 346 (907). 



i Tartar, H. V., "On the Reaction of Sulphur and Potassium Hydroxide in 

 Aqueous Solution." Jour. Am. Chem. Soc., Vol. XXXV, No. 11, page 1741 

 (1913). 



