SECT. II.] 



PROPERTIES OF STEAM. 



71 



102. The force of steam at high temperatures is still wanting to complete 

 the experimental part of the inquiry. A few experiments have been made, which 

 appear to me to be entitled to some confidence, by Professor Arsberger, of Vienna. 1 



ARSBERGER'S EXPERIMENTS ON HIGH PRESSURE STEAM. 



Here the rule is in excess at 432 by more than one sixth ; but in an ex- 

 periment reported by M. Clement, to M. Poisson, * the force of steam at 419 

 is said to be 35 atmospheres, or 1050 inches of mercury, while our rule gives only 

 635 inches. I doubt the accuracy of the statement. 



103. M. Cagniard de la Tour 3 made some essays to ascertain the space and 

 temperature in which a given quantity of water became wholly steam ; but from 

 the frequent rupture of the glass tubes, and their loss of transparency, it was 

 difficult to obtain a result. He states, however, that at a temperature but little 

 removed from the melting point of zinc, water could be converted into vapour in 

 a space nearly four times its volume. If this could have been really ascertained 

 with accuracy, it would have given an important datum ; but on the above rude 

 approximation no reliance can be placed. * 



1 Bulletin des Sciences Tech. vol. i. p. 294. - Philosophical Magazine, vol. Ixi. p. 60. 



3 Philosophical Magazine, vol. Ixi. p. 58. 



4 In a paper on the elastic force of steam which has just been published by Mr. Ivory, in the 

 ' Philosophical Magazine,' a completely different process is followed for calculating the force of 

 steam from that I have given ; it does not however afford results much nearer to the experiments 

 it is founded on, than those by my formula, while it is somewhat more difficult to apply, and 

 becomes erroneous in high temperatures. 



Counting t the temperature from 212 and/ the elastic force, his formula is 



log.^- = -0087466 t - -000015178 t*+ 000000024825 1*. 



tJ\J 



It is derived from a comparison of Dr. Ure's experiments ; and the following table shows the 

 results by those experiments, by Mr. Ivory's formula, by other experiments, and by my formula. 



