Il8 CALORIFIC POWER OF FUELS. 



is used in computing the results. It is, however, by no means 

 certain that the sample represents the average quality of the 

 steam in the pipe from which the sample is taken. The prac- 

 tical impossibility of obtaining an accurate sample, especially 

 when the percentage of moisture exceeds two or three per 

 cent, is shown in the two papers by Professor Jacobus in 

 Transactions * vol. XVI. pages 448, 1017. 



" In trials of the ordinary forms of horizontal shell and of 

 water-tube boilers, in which there is a large disengaging sur- 

 face, when the water-level is carried at least 10 inches below 

 the level of the steam outlet, and when the water is not of a 

 character to cause foaming, and when in the case of water- 

 tube boilers the steam outlet is placed in the rear of the mid- 

 die of the length of the water-drum, the maximum quantity 

 of moisture in the steam rarely, if ever, exceeds two per cent ; 

 and in such cases a sample taken with the precautions speci- 

 fied in article XIII. of the Code may be considered to be an 

 accurate average sample of the steam furnished by the boiler, 

 and its percentage of moisture as determined by the throttling 

 or separating calorimeter may be considered as accurate within 

 one half of one per cent. For scientific research, and in all 

 cases in which there is reason to suspect that the moisture 

 may exceed two per cent, a steam-separator should be placed 

 in the steam-pipe, as near to the steam outlet of the boiler as 

 convenient, well covered with felting, all the steam made by 

 the boiler passing through it, and all the moisture caught by 

 it carefully weighed after being cooled. A convenient method 

 of obtaining the weight of the drip from the separator is to 

 discharge it through a trap into a barrel of cold water stand- 

 ing on a platform scale. A throttling or a separating calo- 

 rimeter should be placed in the steam-pipe, just beyond the 

 steam-separator, for the purpose of determining, by the 

 sampling method, the small percentage of moisture which 

 may still be in the steam after passing through the separator. 

 * Transactions A. S. M. E. 



