44 Transaction*. 



To determine which coal is the most economical to use, 

 actual boiler tests must be made on each variety as received. 

 Combined with the boiler test should be careful chemical 

 analyses, which will furnish standards of quality for future 

 reference. Alone, chemical analyses are not sufficient, as every 

 boiler requires a particular variety of coal for the production 

 of best results, and then a coal can be selected from which 

 the maximum capacity of heat can be obtained ; but, as 

 stated before, this can only be determined accurately by 

 means of actual boiler tests, and subsequently by chemical 

 analyses. 



Particularly in rapidly determining the heat-value of suc- 

 cessive consignments of the same coal, or of similar coals, the- 

 quantity of ash forms the readiest basis of comparison. The 

 ash-deterrnination can be made accurately and rapidly, where 

 it is impracticable to make calorimetric determinations suffi- 

 ciently often.* Coal high in ash has its fuel-value per ton 

 diminished, and, allowing for the moisture, any variation in 

 the quantity of ash gives a sufficiently good criterion of the 

 variation in calorific value. As the ash accumulates, and is 

 mixed with smaller particles of coal, preventing their complete 

 combustion, the grate is stopped up, thus diminishing the rate 

 of combustion and the steam produced. 



From actual calorimetric determinations, compared wirh 

 the ash-determination of various lots of coal of the same class, 

 the following results show that as the ash increases so the 

 calorific value diminishes, the calculations being made on a 

 2-per-cent. -moisture basis. 



Of thirty-two samples of coal examined in this way, twenty- 

 seven, or 84 per cent., varied as above. 



As it costs money to handle ash, coals with a high 

 percentage of ash are also more expensive from this stand- 

 point. 



Another important factor to be considered is the fusibility 

 of the ash. Coals containing much sulphur produce an asn 

 which is readily fusible, and may thus choke up the grate 

 completely. The completeness of combustion depends greatly 

 upon the absence of fusion in the ash, as, in fusing, the asn 



* Jour. Soc. Chem. Ind., 1904, p. 11. 



