270 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE, 



cleaning the grain and preventing the wind dissemination of smut 

 spores. 



In the studies of explosions in grain-handling plants, the bureau 

 has been able to determine a number of the caus-^s and develop ef- 

 fective control methods. Special experimental work has shown that 

 the breaking of electric lamp bulbs in dust clouds has been responsi- 

 ble for a number of explosions, and, in cooperation with the manu- 

 facturing companies, special equipment consisting of a vapor-proof 

 bulb, properly guarded, has been developed and recommended. 

 These recommendations are covered in Department Circular No. 171. 

 It has also been found that explosions can be controlled by the use 

 of inert gases for the prevention of flame propagation. The bureau 

 has shown that by reduction of the oxygen content and the introduc- 

 tion of carbon dioxide the explosion can be confined locally and the 

 extent minimized. 



Attention has been given to the design and development of a rotor 

 separator which can be attached to suction fans to prevent the pass- 

 ing on to the dust collector of any grain drawn in with the dust-laden 

 air. A patent has been granted on the attachment and preliminary 

 tests with a small model justify further tests under actual operating 

 conditions. 



The explosive limits indicating the amount of dust and air neces- 

 sary to form an explosive mixture have been determined for a num- 

 ber of dusts. It appears that the various kinds of dusts have various 

 ranges of explosibility similar to various gases. It lias been de- 

 termined that as small an amount as 0.02 ounce j)er cubic foot will 

 form an explosive mixture of grain dust and air. 



As a result of the bureau's work on the subject, the industrial 

 commissions, safety associations, and insurance organizations of 

 the United States and Canada have made applications of the pre- 

 ventive methods already developed, with the result that the impor- 

 tance of the problem is being well recognized and tlie bureau is being 

 constantly called upon to test various kinds of dust to determine 

 their explosibility and to suggest control methods. Recent ex- 

 plosions of new kinds of dust havje been occurring, and the bureau 

 has been called upon to study a series of explosions of lime-sulphur 

 and insecticide dust being manufactured in powdered form. Special 

 assistance has been given to the industrial commission of Wisconsin 

 in a study of dust-control methods in grain elevators in line with 

 efforts being made by the Canadian Government and safety organiza- 

 tions in the United States. 



A large number of bulletins, circulars, pamphlets, leaflets, and 

 cards have been issued by the bureau dealing with the causes of 

 these explosions as they have been established by investigation and 

 with control methods that have been determined by experimental 

 work. There lias been an active demand by the agricultural inter- 

 ests and the industries of the country for these publications, and they 

 have been the basis of State and municipal control and supervision. 



UTILIZATION OF FRUITS AND VEGETABLES. 



Work on the factory production of sweet-potato sirup at Fitz- 

 gerald, Ga., w^as completed during the year and a report prepared 

 for publication. This report give's all of the data developed in the 



