1922] 



YOUNG — THE TOXIC PROPERTY OF SULPHUR 431 



while hot into solution I. After diluting solutions I and II each 

 with 4 liters of water they are mixed and let stand for 3-18 hours 

 when the mixture is ready for use. It is somewhat unstable 

 and should be used within a few days, preferably the next morn- 

 ing. 



Kuhl ('21) experimented with De Haen's colloidal soluble sul- 

 phur * and found it to be very effective in controlling mildews 

 and related diseases. He stated that the mixture was very ad- 

 hesive and that it did not burn the leaves. He believed that the 

 increased effectiveness of this type of sulphur over other sulphur 

 sprays was due to its increased chemical activity. 



Barker and Wallace ('22) describe a new method for sulphur 

 fumigation for the greenhouse. In previous studies they found 

 that the fungicidal value of sulphur depended upon its being ap- 

 plied as extremely finely divided particles. Their method is as 

 follows: Air is passed through molten sulphur in a Campbell's 

 "sulphur vaporiser," the temperature of the sulphur being kept 

 just above the melting point and well below the ignition point. 

 The melting point of sulphur is about 115° C. and its ignition 

 point in the air is about 260° C. The most satisfactory tem- 

 perature is around 170° C. Under these conditions an abun- 

 dant cloud of sulphur in the particulate condition is produced. 

 An improvement in the yield of particulate sulphur is effected 

 if the current of air is passed into the molten sulphur through 

 a perforated nozzle. By means of an attached delivery tube the 

 particulate sulphur can be discharged in any given direction and 

 on to any definite object. It can be used for general fumigation 

 or for direct spraying. 



Another method for fumigation has been described by Vogt 

 ('21), and is as follows: Three-hundred gms. of pure roll sulphur 

 (stick sulphur) contained in a small iron pan is liquefied and 

 brought to the boiling point (448° C). There is heated at the 

 same time in a circular copper boiler 400 gms. of water. The 

 strongly superheated steam of the latter is forced under high 

 pressure through the boiling sulphur which vaporizes it into 

 small mist-like drops. These drops preserve their liquid form for 

 several hours. They possess a high degree of adhesion not other- 

 wise common to sulphur and do not burn the leaves. A few 

 gms. of sulphur are enough to fill an average greenhouse with 

 clouds of vapor which in a very short time covers all free surfaces. 



1 Manufactured by De Haen at Seelze. 



