THE TOXIC PROPERTY OF SULPHUR 1 



HARRY CURTIS YOUNG 



Research Fellow in the Henry Shatv School of Botany of Washington University 2 



Introduction 



Since the introduction of spraying for the control of parasitic 

 fungi there has been developed a large number of fungicidal 

 mixtures. Some have proved effective for the control of one 

 organism and some for another, none of them having universal 

 fungicidal value. Because of its abundance, low cost, and its 

 effectiveness under certain conditions, sulphur has been employed 

 in many of these mixtures. The fact that it has toxic or fun- 

 gicidal properties has been conclusively demonstrated. In this 

 work, an attempt has been made to determine if possible the 

 exact nature of this fungicidal property, that is, to determine 

 or evaluate the chemical compound or compounds in which this 

 toxic property is resident, at the same time to relate this toxic 

 property to conditions under which it may be consistently mani- 

 fest, thus warranting its general use as a fungicide. 



The use of sulphur as a fungicide probably antedates that 

 of all other substances. The chemical and physical properties 

 of sulphur, especially its existence in so many forms, have led 

 to its employment as a fungicide in a variety of ways. Regardless 

 of the form in which it is employed, whether as a compound 

 or as uncombined sulphur, there seem to be necessary certain 

 chemical or physical changes before its toxic properties are ex- 

 hibited. Toxicity has been attributed to many of the forms, 

 for example, to such products of combined sulphur as various 

 sulphides, thiosulphates, sulphur dioxide, sulphuric and sulphur- 

 ous acids, and also to uncombined sulphur as flowers, or even as 

 sulphur in a more finely divided state, that is, as colloidal sulphur. 

 However, there seems to be no tangible evidence in the past 

 work that toxic properties can be attributed directly to any one 

 of these forms, the presence of which might thus determine its 



;es in which sulphur 



gicide 



matter of considerable 



'An investigation carried out at the Missouri Botanical Garden in the 

 Graduate Laboratory of the Henry Shaw School of Botany of Washington 

 University, and submitted as a thesis in partial fulfillment of the requirements 

 for the degree of doctor of philosophy in the Henry Shaw School of Botany of 

 Washington University. 



A fellowship established by the Crop Protection Institute for the investiga- 



tion of sulphur as a fungicide. 



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