Mechanical Integration of the Product of two Functions. 141 



7. Mercury and Water. From determinations of vapour- 

 pressures of mercury by Ramsay and Young *. If Regnault's 

 values are correct, the equation W — H + c(t f — t) does not 



hold good. Values of -~- . t for water taken as unity at 



each pressure. Temperatures of water as ordinates. 

 c= -0-0004236. 





Reduced ratios of -±- . t. 



f.tioi 



Mercury. 



Pressures. 



dt 



dt 





Calculated. 



Recalculated. 



Calculated. 



Recalculated. 



millim. 











10 



•866 



•8600 



160 



158-9 



50 



•850 



•8486 



714 



713-2 



100 



•833 



•8429 



1339 



1355 



150 



•843 



•8393 



1950 



1943 



200 



•835 



•8366 



2519 



2523 



300 



•834 



•8326 



3639 



3631 



400 



•827 



•8296 



4682 



4696 



500 



•827 



•8272 



5715 



5714 



600 



•829 



•8252 



6741 



6714 



700 



•824 



•8234 



7731 



7723 



800 



•829 



•8218 



8717 



8647 



900 



•814 



•8204 



9621 



9701 



1000 



•818 



•8191 



10595 



10607 



1500 



•811 



•8139 



15064 



15112 



2000 



•816 



•8099 



19633 



19494 



3000 



•804 



•8040 



27919 



27928 



5000 



•800 



•7958 



43562 



43356 



8. Mercury and Carbon Bisulphide. Employing the values 



of ~- . t for mercury and carbon bisulphide, both recalculated 



from their ratios with those of water, these values bear an 

 almost constant ratio to each other at all pressures, or c = 0. 

 The calculated ratios vary only between 1*0547 and T0552. 



XIX. Mechanical Integration of the Product of two Functions. 



To the Editors of the Philosophical Magazine and Journal, 

 Gentlemen, 



IN connection with my paper (Phil. Mag. August 1885) on 

 the mechanical integration of the product of two functions, 

 Professor Nanson, of the Melbourne University, has sent me 

 the following suggestion by which the necessity for the special 

 piece of mechanism there described is obviated. 



cj)(6)^r(0)cW be required; plot the two curves 



f 



r=<Kff)+ir(e), r = <K0)-f(0); 



The data for these determinations are to be found in the l Journal 



of the Chemical Society/ January 1886. 



