Manchester Memoirs, Vol. xli. (1896), No. 3. 5 



But any attempt to estimate the percentage of water in 

 the sample involves the subsequent condensation and 

 weighing of the steam in the sample as well as the drained 

 water, which are difficult and complicated operations. 

 Besides this, the pressure in the steam pipe near the 

 engine is generally subject to considerable periodic altera- 

 tions owing to the intermittent and periodic demand for 

 steam in the engine, which introduces complications of 

 unknown extent. ^ 



Wire-drawing C a lorimeters . 



With a view to obtaining a test for the samples of 

 steam which should be independent of the separator, the 

 so-called Wire-drawing Calorimeter has been introduced. 

 In this, the sample of steam, whether it has been first 

 drained or not, is received quietly in a vessel at the same 

 pressure as the steam pipe, where it is at steady known 

 pressure; from this it is allowed to escape continuously 

 through a small orifice into a second larger vessel, main- 

 tained at greatly lower pressure than the first. In this its 

 temperature and pressure are measured, the steam then 

 passing on into a condenser or into the atmosphere. 



The quantity of water present is then estimated from 

 the observed pressures in the two vessels, and the difference 

 between the observed temperature in the second vessel 

 and the temperature of saturation at that pressure, as 

 taken from Regnault's tables. 



Such calculations are at once seen to be based on 

 Regnault's determination of the relations between the 

 pressure and temperature of saturated steam, together 

 with the heat relations, whatever they may be, between 

 saturated steam and superheated steam. And, as the 

 second relation does not appear to be known except as 

 a very rough approximation, the results so obtained must 

 be doubtful. 



