Thermo-electric Action of Metals in Electrolytes. 255 



of the galvanometer needle, with a solution containing '3 grain of the 

 salt per ounce of water being TO, with '6 grain 2'0, 6'0 grains 8'25, 

 and 12'0 grains ll'O. The hot platinum was positive. With mercury 

 at those temperatures, in solutions of "5 grain, 5'0 grains, and 

 lO'O grains of that salt per ounce of water, the hot metal was 

 negative, and the deflections were 14'0, 45*0, and 50*0 respectively.* 



The first point to be observed with regard to the table is, that out 

 of 286 instances contained in it, including an average variety of 

 liquids of alkaline, neutral, and acid reaction, in 87 or 30'42 per cent, 

 only, or a proportion of 1 to 2'27, was the hot piece of metal negative 

 to the cold one. 



The thermo-electric order of metals in liquids was with every 

 solution widely different from the ordinary thermo-electric order of 

 metals alone, with no one liquid did more than three out of the 

 thirteen metals agree in position in both the orders. It is remarkable 

 that magnesium, a metal so very corrodible, so highly chemico-electro- 

 positive, and so considerably thermo-electro-positive, in the series of 

 metals only, is so often the most thermo-electro-negative in these 

 series ; in each case however where magnesium was at or near the 

 bottom of the thermo-electric series, it was covered with a thin film 

 of insoluble matter (see also pp. 261, 270, and 278). 



The following list of the number of times each metal was positive 

 and negative in Table I is inserted for future reference : 



199 87 



Proportion 2'287 to TO. 



* See " Proc. Roy. Soc.," No. 199, 1879, Experiments 1 4. Mercury was tried 

 in a different apparatus. 



