Prof. R. Buusen's Spectral- Analytical Researches. 419 



K 2 O.Cr 2 0,] K 2 O.S0 3 , 

 3Zn l=3ZnO.S0 3 , 



6H 2 O.S0 3 J Cr a 3 .2S0 8 . 



K 2 O.Cr 2 6 l K 2 O.S0 3 , 

 3Zn l=3ZnO.S0 3 , 



7H 2 O.S0 3 | Cr 2 3 .3S0 3 



With the liquid employed by Warrington, in accordance with 

 theory (viz. 1 equivalent of dichromate and 4 equivalents of sul- 

 phuric acid), the following reactions take place, if we suppose 

 the clay cells to be removed and both exciting plates to dip into 

 the chromic liquid : — 



KOPrOl *0-429K 2 O.Cr 2 O 6 , 

 WUZn 2 6 I -°' 571 Cr * °* * 3S °3> 

 4Jl 2 U.fcU 3 J 0-571 K 2 O.S0 3 . 



It is evident that in the liquids 1 and 2 the proportion be- 

 tween the constituents before and after decomposition remains 

 unchanged until exhaustion of the battery, and that one of the 

 primary conditions of a constant current is therefore fulfilled — 

 but that, on the other hand, if Warrington's liquid be used with- 

 out clay cells, the original conditions of current-production are 

 no longer present as soon as the consumption of dichromate has 

 reached 57 per cent. This waste, amounting to not less than 

 43 per cent., is accompanied by a yet greater disadvantage, viz. the 

 fact that the acids present at the close of the action are not suf- 

 ficient to form soluble salts with the bases. Deposits are soon 

 formed on the exciting plates, whereby a polarizing action is in- 

 duced which is attended with a diminution of the current. It 

 is not, therefore, to be wondered at that the use of Warrington's 

 liquid in the chromic-acid battery without clay cells gives very 

 unsatisfactory results. Inasmuch as theory does not point out the 

 influence exercised upon current-production by the formation of 

 the green or blue modification of chromium oxide, nor tell the 

 quantity of water to be added in order to ensure the best result, 

 it appeared necessary to decide these points by experiment. 



Ten liquids were prepared by the successive addition of mea- 

 sured quantities of sulphuric acid to Warrington's liquid ; and 

 from each of these, five liquids were prepared by the addition of 

 increasing measured quantities of water. In certain of these 

 liquids, systematically chosen, there was placed a single pair 

 formed of amalgamated zinc and carbon, having a tangent-gal- 

 vanometer in the connecting-circuit, care being taken that the 

 conditions were the same in each case. The intensity of the 

 current was then observed until the battery v/as almost exhausted. 



The best working mixture was found to correspond with that 

 2E2 



