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[Vol. 9 



GARDEN 



crushing yeast cells, was employed. Eight gms. of flowers of sul- 

 phur were mixed with 3- gms. of diatomaceous earth (Kieselguhr), 

 and the mixture ground for 14 hours. One-half gm. of this mix- 

 ture was added to each test-tube containing the slightly buffered 

 solution of the different hydrogen-ion concentrations md the 

 toxicity determined as before. An attempt was made to grind 

 the sulphur without the diatomaceous earth but the sulphur had 

 a tendency to cake and did not grind well. Other substances are 

 being tried with the hope of eliminating diatomaceous earth. Re- 

 sults of this experiment are given in table i, figs. 1-4. 



Sulphur in this state was found to be more toxic than the 

 flowers of sulphur unground. A more marked influence of the 

 hydrogen-ion concentration was noted, the range showing the 

 greatest toxicity being between P H 4.2 and 5.4. The increased 

 toxicity at this point is attributed to one of 2 possibilities: first, 

 the spores may be less resistant at this point, or second, the toxic 

 form or conditions of sulphur may have been produced in greater 

 amounts at this range. At any rate the hydrogen-ion concentra- 

 tion and the fineness of the particle contributed to the in- 

 creased toxicity of the sulphur. The fineness of the particle 

 did not seem to be the direct cause, as germ tubes grew nDrmally 

 after the initial retardation, even though they were directly in 

 contact with the sulphur particles. 



EXPERIMENT 3. COLLOIDAL SULPHUR 



Sulphur readily assumes the colloidal state. The element sul- 

 phur has been known since the beginning of history, and records 

 show that colloidal sulphur was prepared and studied as early 

 as the seventeenth century. "Lac Sulfurus," a colloidal form of 

 sulphur, was prepared in 1765 by Stahl (1766) and was used at 

 that time for medicinal purposes. Fourcroy (1790), Berthollet 

 (1798), Berzelius (1808), and Magnus (1827) were early con- 

 tributors to the study of colloidal sulphur. Present-day methods 

 for the preparation of colloidal sulphur are found in papers by 

 Svedberg ('09), Himmelbauer ('09), Raffo ('08, '11), Ode:i ('13), 

 v. Weimarn and Molyschew ('11), Kelber ('12), and others. 



Colloidal sulphur exists in two forms, depending upon the 

 degree of hydration. The form having a very high degree 

 of hydration will be discussed in this paper as the hydro- 

 philic colloidal sulphur and is identical with the product prepared 

 by Raffo and Mancini ('11) and Oden ('13) and called 'soluble 



