1889.] On the Detection of dissolved Chemical Compounds. 265 



January 17, 1889. 

 Professor G. G. STOKES, D.C.L., President, in the Chair. 



The Presents received were laid on the table, and thanks ordered 

 for them. 



The following Papers were read : 



I. " A Method of detecting dissolved Chemical Compounds and 

 their Combining Proportions." By G. GORE, F.R.S. Re- 

 ceived November 14, 1888. 



(Abstract.) 



The method described and illustrated by examples in this research 

 is an application of the " voltaic balance " to the measurement of the 

 amount of voltaic energy of electrolytes (see ' Roy. Soc. Proc.,' vol. 44, 

 pp. 151 and 294), and is based upon the general truth that "when 

 substances chemically combine they lose some of their power of 

 exciting a voltaic couple," and the amount of this power can be 

 measured by means of the " voltaic balance." (Sketch.) 



The method is briefly as follows : Oppose and balance the current 

 from a small voltaic couple of unamalgamated zinc and platinum in 

 a known quantity of distilled water in a small glass vessel through a 

 sufficiently sensitive galvanometer, by that from a perfectly similar 

 couple, and take care by occasionally heating the platinum to redness^ 

 to avoid error caused by absorption of hydrogen. 



Dissolve in separate, equal, and known quantities of distilled water 

 a series of several mixtures of the two constituents A and B of the 

 supposed compound, in the proportions of their atomic or molecular 

 weights, and multiples of them, some having an excess of A, and 

 others of B. For instance, if both are monads mix them in the 

 several proportions represented by the formulae 5A + 4B, 4A + 4B, 

 and 4A + 5B; but if A is a monad and B a dyad, then use the 

 proportions indicated by 3A+2B, 4A + 2B, and 5A + 2B. 



Add sufficiently minute quantities in succession of one of these 

 solutions to the water of one of the voltaic couples until the needles 

 of the galvanometer visibly commence to move, and note the amount 

 added. Recharge the vessel with distilled water, clean the metals, 

 and repeat the experiment with another of the solutions ; and so on 

 until all the solutions have been tried, and the mixture has been 



VOL. XLV. I 



