544 ANNUAL REPOET SMITHSONIAN INSTITUTION, 1916. 



outfit is shown in plate 7. It weighs approximately 20 pounds. 

 The carrying case is made of §-inch poplar, dovetailed at the corners 

 and brass bound, and is provided with a cover and a handle. The 

 outside dimensions are 7 by 13 by 14 inches high, which is large 

 enough to furnish ample room for all the required apparatus, cans 

 of alcohol, extra supply containers, etc. The outfit consists of the 

 volumeter «, the pipette &, the balance c^, the funnel d., the alcohol 

 can e, the sampling scoop /, the sampling cloth ^, etc. 



A determination of the percentage of combustible matter in a given 

 sample of dust is made as follows: 



Twenty-five cubic centimeters of alcohol is measured into the 

 volumeter flask with the pipette; 20 grams of the dust to be tested 

 is then poured in. The graduated tube is inserted in the flask, and 

 the dust and alcohol are thoroughly mixed by shaking, after which 

 25 cc. more of alcohol is added from the pipette through the stem 

 of the volumeter, all adhering particles of dust being carefully 

 washed down. 



After one minute the scale reading of the meniscus is taken, and 

 by reference to tables the percentage of noncombustible is obtained. 



The placing of this apparatus at the disposal of the employees of 

 the bureau will enable them to determine whether the dust hazard 

 in any mine in their district is such as to warrant treatment to prevent 

 a dust explosion. 



It is further expected that when tliis apparatus becomes available 

 for genera] use it may result in calling the attention of mine oper- 

 ators to dangerous dust conditions that might otherwise eventually 

 cause disastrous explosions. 



