BUREAU OF CHEMISTRY. 357 



be conceived as being of a twofold nature, (i) to carry on a type of 

 research work which industrial and agricultural industries, State 

 safety commissions, insurance associations or individuals can not 

 perform, on problems of a physical-chemical nature, for the pre- 

 vention and control of dust explosions, with the development of the 

 proper instruments and devices for this purpose, and {2) to render 

 expert advice, after proper testing, on the explosion hazards of dusts 

 and powdered materials submitted by the agencies mentioned. 



Instruments to determine the quantity of dust in the air are being 

 devised. Determinations of the percentage of combustible and non- 

 combustible constituents of dusts are made. 



The bureau cooperates with national and commercial organiza- 

 tions interested in the reduction of fire and explosion losses, such as 

 the National Fire Protection Association, National Safety Council, 

 National Board of Fire Underwriters, Underwriters' Laboratories, 

 Chamber of Commerce of the United States, and State industrial 

 and welfare commissions. 



Fires in cotton gins and cottonseed-oil mills. — As a result of in- 

 vestigational and experimental work at cotton gins in the South- 

 west during the 1922 ginning season, an improved and simplified 

 grounding system for the control of static electricity during ginning 

 operations was devised. The results of this work were published in 

 Department Circular 271, Grounding Cotton Gins to Prevent Fires. 

 Negotiations for the complete recognition of the effectiveness of the 

 grounding system recommended were undertaken with the State 

 Insurance- Commission of Texas and various companies under- 

 writing cotton gins in that State. As a result it is expected that the 

 insurance rates on gins in Texas will be further revised, provided 

 the gins are adequately grounded. Such recognition has already 

 been given in a number of Southeastern States. 



Preliminary investigations relating to a study of fires in cotton- 

 seed-oil mills were conducted during the early part of the milling 

 season. Keports were received of approximately 20 fires in southern 

 cottonseed-oil mills, with a loss aggregating $900,000. Approxi- 

 mately two-thirds of these fires occurred in Texas oil mills. 



Explosions and fires in threshing machines. — Furtlier recognition 

 of the dust-collecting fans developed by the department, in co- 

 operation with various manufacturers of threshing machinery, has 

 resulted in a natural saving to farmers in rates for insurance. In- 

 surance rates for the 1923 season in the State of Washington were 

 reduced an additional $2 per $100 of insurance for grain threshing 

 machines fully grounded and properly equipped with an effective fan. 

 The original rate in the Pacific Northwest was approximately $11 per 

 $100, while the new rate made effective June 21 is $7 per $100, a 

 reduction of $4 per $100. Arrangements have been made for the 

 manufacturing companies to construct fans embodying the specifi- 

 cations worked out by department engineers, and the bureau is co- 

 operating with the State fire marshal of Washington and other State 

 officials in this work. 



DEHYDEATION OF FRUITS AND VEGETABLES. 



Under an authorization for the study and improvement of 

 methods of dehydrating materials used for food and to disseminate 



