2 MR. J. H. GRINDLEY ON AN EXPERIMENTAL INVESTIGATION OF 



theory of the properties of steam, as at present accepted, and all the steam tables are 

 founded on the experiments of REGNAULT on the total heat of evaporation, so that if 

 any other definition is given of saturated steam than that which results from boiling 

 the water under constant pressure after it has been drained of entangled water by 

 gravitation, these properties and tables will not apply." In the same paper Professor 

 REYNOLDS describes a method of experimenting in which it is sought to determine 

 whether, by sufficient wiredrawing of saturated steam at a known initial pressure and 

 temperature, the steam could be finally brought into the condition of steam gas. 



Having undertaken the experimental verification of the conclusions given in 

 Professor REYNOLDS'S paper, the author begs to point out the significance of the 

 above extract in relation to any work which may be done in this subject, and to 

 remark that it governs the methods and principles which have been adopted in the 

 research, the results of which it is the object of this paper to describe. 



The method given by Professor REYNOLDS is briefly as follows. If saturated steam 

 be wiredrawn by passage through a small orifice from one chamber in which the 

 pressure can be kept constant to another in which the pressure can be adjusted to 

 have any lower value required, the steam in the second chamber will become super- 

 heated, and at first the temperature will fall, but if the pressure can be so far reduced 

 in the second chamber that the amount of superheat contained by the steam is 

 sufficient to render it perfectly gaseous, the temperature will be then unaffected by 

 any further reduction in the pressure in the second chamber. Whether this " perfect 

 gas " condition can be reached, by wiredrawing saturated steam from pressures up to 

 200 Ibs. per square inch, is the question which it is the primary object of the present 

 research to decide. 



Before proceeding, however, very closely into the research, an examination of the 

 theory of such wiredrawing experiments will reveal a point which would require 

 definite settlement before the method described above could be adopted. In reducing 

 the results of any wiredrawing experiments it would be necessary to know, or to 

 possess some knowledge of, the precise law of flow which the steam obeys during its 

 passage through the orifice. The usual theory adopted assumes that this law is the 

 adiabatic one for saturated steam, but whether adiabatic flow is ever obtained in 

 actual wiredrawing experiments is as yet undecided, and will, as mentioned above, 

 require definite settlement. 



Hence the author was recommended by Professor REYNOLDS to preface the research 

 by an independent investigation into the laws governing the flow of steam through 

 orifices of different natures. If it could be shown that the law of flow was never 

 truly adiabatic, then the results of any wiredrawing experiments would not be 

 capable of easy or accurate reduction to yield the thermodynamical properties which 

 superheated steam possesses, but if such flow could be shown under certain circum- 

 stances to be adiabatic, then under these conditions the reductions would be both 

 easy and direct. 



