MOISTURE IN THE STEAM. 1 1/ 



To measure the temperature by pressure an air-thermom- 

 eter is used. A registering manometer aids the work consid- 

 erably, as observations should be taken regularly at frequent 

 and equal intervals. The temperature is calculated by means 

 of tables of vapor-tension.* 



MOISTURE IN THE STEAM. 



The percentage of moisture should be ascertained by 

 means of a throttling or a separating calorimeter, directions 

 for the use of which will be furnished by the makers. They 

 should easily and completely separate the water in a manner 

 convenient for measuring, or better, for weighing. It is ad- 

 visable to use two or three at the same time, thus serving as 

 checks for each other. 



" The throttling steam-calorimeter was first described by 

 Professor Peabody in the Transactions^ vol. X. page 327, 

 and its modifications by Mr. Barrus, vol. XI. page 790; vol. 

 XVII. page 617; and by Professor Carpenter, vol. XII. page 

 840 ; also the separating-calorimeter designed by Professor 

 Carpenter, vol. XVII. page 608. These instruments are used 

 to determine the moisture existing in a small sample of steam 

 taken from the steam-pipe, and give results, when properly 

 handled, which may be accepted as accurate within 0.5 per 

 cent (this percentage being computed on the total quantity of 

 the steam) for the sample taken. The possible error of o. 5 

 per cent is the aggregate of the probable error of careful ob- 

 servation, and of the errors due to inaccuracy of the pressure- 

 gauges and thermometers ; to radiation ; and, in the case of 

 the throttling-calorimeter, to the possible inaccuracy of the 

 figure 0.48 for the specific heat of superheated steam, which 



* For full details regarding setting up an open-air manometer, see paper 

 by Scheurer-Kestner and Meunier-Dollfus in the Bulletin de la Socie'te' in- 

 dustrielle de Mulhouse, 1869, page 241; also Trans. A. S. M. ., vol. vi. 

 pages 281 and 282. 



f Transactions A. S. M. E. 



