.18 MASS. EXPERIMENT STATION BULLETIN 24-8 



Rupprecht (29) and Vogt (31.) reported a portable apparatus, the Rota- 

 Generator, so constructed as to prevent the oxidation of sulfur by generating 

 non-oxidized sulfur vapors under the exclusion of air mixed with steam en- 

 tering under pressure. The gulfur vapors which otherwise would issue slowly 

 are forced out rapidly by steam blasts. The merits claimed for the device 

 are safety of operation, rapid production of vapors, and the extreme fineness 

 of the sulfur. According to Vogt (36) the expectations which some thought 

 were to be realized by this invention have not materialized. It is adapted only 

 to greenhouses, and here its practical value is questionable since inter- 

 ruptions occur in its operation because of mechanical complications in con- 

 struction. 



Imj)roved sulfur vaporizers. The lack of adaptation or acceptance of the 

 patented types of vaporizers led to the study of equipment suitable and prac- 

 tical for use in greenhouses in Massachusetts. 



In Massachusetts, electricity is employed for lighting purposes in prac- 

 tically all greenhouse establishments although only the boiler and packing 

 rooms are wired. The writer conceived the idea of vaporizing sulfur in por- 

 celain evaporating dishes on electric hot plates. The flat heating surface of 

 the hot plate was covered with a square of i/4 inch asbestos board with a 

 hole 41/0 inches in diameter in which was set a round-bottom porcelain evap- 

 orating dish (Plate II A). Two heavy copper insulated wires of No. 6 

 gauge were installed along the entire length of the greenhouse. At frequent 

 points on the wires electric sockets were connected, into which the hot plates 

 were plugged (Plate II B and C). With a suflBcient source of electric cur- 

 rent, houses of any capacity may be treated with vaporized sulfur in this 

 manner. Where several large houses comprise the range a power line con- 

 nected with each house would appear to be most satisfactory. On the other 

 hand, in a range with houses 200 x 30 feet, and with a 25 ampere meter and 

 No. 30 fuses, the lighting circuit should offer sufficient electric current. In 

 any event a strong current is necessary to produce the heat required for 

 vigorous fuming of the sulfur. 



The cost of the heating equipment is small. The electric plates retail for 

 $1.00 each, and evaporating dishes 185 mm. in diameter, 50 mm. deep and 

 765 ml. capacity, for $1.08. The price of V4 inch asbestos board is $0.20 per 

 pound. The total cost of each unit excluding wires and socket fixtures is 

 about $2.15. When operated on a power line the cost of operation is much 

 less than if on a lighting circuit. The economy and convenience of this method 

 of controlling Cladosporium leaf-mold is appealing. 



A sulfur vaporizer designed by the writer and embodying the principle 

 involved in the Rota-Generator but simpler of construction has been used 

 (Plate II D). Water is contained in a cylindrical copper tank, the center of 

 which is provided with a sulfur receptacle of heavy Pyrex glass. Both 

 water and sulfur are heated by an electric hot plate and the steam gen- 

 erated is blasted into the molten sulfur through a metal tube. The sulfur 

 vapors are discharged much more rapidly than with the other apparatus de- 

 scribed. The glass sulfur receptacle is undesirable and the metal steam 

 conductor is acted upon by molten sulfur. If these objectionable mechanical 

 features can be overcome this apparatus would prove highly satisfactory for 

 commercial purposes. 



Greenhouse Tests. 



A series of control experiments were instituted at the Market Garden Field 

 Station greenhouse at Waltham and at the range of Wm. H. Derby, Melrose, 



