344 REPORT— 188T. 



For the purpose of controlling the results, samples one and five were taken 

 from the molten metal while no current was passing and were assayed with the 

 rest. It will he seen from the above table that the difierence varied from a mini- 

 mum of one ten-thousandth as deduced from the total difference found on assaying 

 samples two to four, to a maximum of five ten-thousandth presented by sample 

 two. The alloys of lead with two per cent, of silver and with 51 per cent, of 

 silver also gave negative results, and experiments as a whole, so far as they have 

 yet been carried, tend to show that an alloy conducts metallically, and that its 

 constituents cannot be separated by an intense electric current. The experiments, 

 however, can only be considered to be preliminary. They must be repeated and 

 extended, and alloys of which arsenic is a constituent must be tried, and further, it 

 is specially important to examine the behaviour of such alloys as those of tin-cop- 

 per and bismuth-gold, as certain members of both series show marked points on 

 the curves representing the electrical resistance which would appear to indicate the 

 existence of definite compounds. 



On the Action of an Electric Current in hastening the Formation of Lagging 

 Compounds. By Dr. J. H. Gladstone, F.B.8. 



When two salts ui solution, MR and M'R', are mixed together they partially 

 decompose one another, the proportions of the resultbg four salts MR, MR', M'R, 

 M'R', depending upon their relative masses and relative affinities. When one of 

 these salts is insoluble, it separates as an amorphous or crystalline precipitate, and 

 the redistribution goes on until the largest possible quantity of it is formed and 

 precipitated. This reciprocal decomposition generally takes place very rapidly, but 

 in some cases it proceeds slowly enough to be watched and measured. While 

 investigating this subject a good many years ago, I made some experiments on the 

 physical forces that accelerate or retard this action, and among them I tried 

 the influence of a voltaic current passing through the mixture. I used a small 

 Grove's battery with narrow platinum poles. 



1. The first experiment was made with a mixture of tartaric acid and nitrate of 

 potassium. The strength of the tartaric acid was 4-5 grammes, and of the nitrate 

 of potassium 1-02 grammes to 1,000 grain measures {i.e. 64'8 cubic centimeters) of 

 water ; and the proportions used were three equivalents of the acid to one of the salt. 

 In a comparative experiment four minutes elapsed before crystals began to appear. 

 On making the current, the pole from which oxygen gas was being slowly evolved 

 became immediately coated with potassic bitartrate, and crystals formed throughout 

 the liquid between the poles. 



2. A similar result was obtained with potassic oxalate and magnesic sulphate. 



3. A mixture of single equivalents of magnesic sulphate and oxalate of ammonium 

 was divided into two portions. Through the one a weak current was passed, and 

 after a few minutes a cloudiness appeared, extending in lines from the one pole to 

 the other, and not below the poles. As yet there was no cloudiness whatever in 

 the comparative experiment. 



4. A similar result was obtained with a mixture of calcic sulphate and strontium 

 nitrate, but the lines of cloud extending from the oxygen towards the hydrogen 

 pole were stiU more remarkable. The comparative mixture was quite clear. 



5. A mixture of citrate of iron and meconic acid goes on increasing in redness 

 for some time, but in this case all the compounds are soluble in water. No 

 acceleration seemed to result from the passage of the galvanic current. 



6. A mixture of citrate of iron and ferrocyanide of potassium shows a gradual 

 formation of the blue ferrocyanide. This was hastened by the galvanic current ; 

 but there is this objection to the experiment, that the ferrocyanide itself was some- 

 what decomposed. 



Last autumn a neighbour of mine, Mr. J. Enright, wrote to me to the follow- 

 ing purpose : — ' Thinking one day some few months ago over the decompositions 

 and recompositions which we figure to om-selves as going on in an electrolytic salt, 

 it occurred to me that we might get some confirmation, or the reverse, of them from 



