APPENDIX. 189 



moisture. For these latter coals it is important that a more 

 accurate method be adopted. The method recommended by 

 the Committee for all accurate tests, whatever the character 

 of the coal, is described as follows : 



Take one of the samples contained in the glass jars, crush 

 the whole of it by running it through an ordinary coffee-mill 

 adjusted so as to produce somewhat coarse grains (less than 

 T V inch), thoroughly mix the crushed sample, select from it a 

 portion of from 10 to 50 grams, weigh it in a balance which 

 will easily show a variation as small as I part in 1000, and 

 dry it in an air or sand bath at a temperature between 240 

 and 280 degrees Fahr. for one hour. Weigh it and record 

 the loss, then heat and weigh it again repeatedly, at intervals 

 of an hour or less, until the minimum weight has been 

 reached and the weight begins to increase by oxidation of a 

 portion of the coal. The difference between the original and 

 the minimum weight is taken as the moisture. This moisture 

 should preferably be made on duplicate samples, and the 

 results should agree within 0.3 to 0.4 of one per cent, the 

 mean of the two determinations being taken as the correct 

 result. 



If the coal contains an appreciable amount of surface 

 moisture, another portion of the 100 pounds sample should 

 be weighed and spread out in a thin layer on a clean sheet- 

 iron plate, and exposed for a period of twenty-four hours to 

 the atmosphere of the boiler-room, and by this means air- 

 dried. After being weighed again, the percentage which the 

 weight shrinks during this drying may be termed the percent- 

 age of surface moisture. 



XV. Treatment of Ashes and Refuse. The ashes and 

 refuse are to be weighed in a dry state. For elaborate trials 

 a sample of the same should be procured for analysis. When 

 it is desired to know accurately the amount of coal consumed, 

 as distinguished from combustible, all lumps of unconsumed 



