American Journal of Science, dfc. 149 



Character of the zinc plates. — If pure zinc could be obtained it 

 would be highly advantageous, as tbe foreign metals, such as copper, 

 lead, iron, cadmium, &c, which are left on the surface of the acid, 

 to whose action it is exposed, diminish the effect of the action. The 

 purest zinc of commerce is the rolled Liege or Mosselman's zinc. 

 After being used, the plates of a battery should be cleaned from the 

 metallic powder on their surfaces. No old charge containing copper 

 should be used to excite a battery. New plates are much more 

 powerful than such as have been used. The first time, 20 pairs of 

 4 inch plates in porcelain troughs were used, they lost per plate, only 

 3-7 atoms ; but after that the loss was 5*25 to 5-9 atoms. 



Vicinity of the copper and zinc. — When the copper and zinc are 

 near to each other, the power is not only greater at the instant, but 

 also, the sum of transferable power, in relation to the whole sum of 

 chemical action at the plates, is much increased ; because, whatever 

 tends to retard the circulation of the transferable force, (viz. electri- 

 city), diminishes the proportion of such force, and increases the pro- 

 portion of that which is local. Now, the liquid in the cells produces 

 this retarding power, and, therefore, acts injuriously, in greater or 

 less proportion, according to the quantity of it between the zinc and 

 copper plates, i. e. according to the distances between their surfaces. 

 The superiority of double coppers, also, depends, in part, upon 

 diminishing the resistance offered by the electrolyte between the 

 metals. The great effect, on first immersion, is owing to the un- 

 changed condition of the acid, the effect of which diminishes as it 

 becomes neutralized. 



Number and size of plates. — The author found that the consump- 

 tion of zinc, arranged as 20 plates, was more advantageous than if 

 arranged either as 10 or 40; and also, that increase of numbers 

 did not improve the effective production of transferable chemical 

 pony r, from the whole quantity of chemical force active at the sur- 

 faces of excitation. If, in a particular case, the most effectual number 

 of plates is known, then the addition of more zinc would be most 

 advantageously made in increasing the size of the plates, and not 

 their numbers. At the same time a large increase in the size of the 

 plates would raise, in a small degree, the most favourable number. 

 Large and small plates should not be used together. 



Simultaneous decompositions. — When the number of plates much 

 surpasses the most favourable proportion, two or more decompositions 

 may be effected, and simultaneously, with advantage. Thus 40 pairs 

 of plates produced 22-8 cubic inches of gas in one volta electrometer ; 

 when re-charged, they produced 21 inches in each of 2 electrometers. 

 When 20 pairs of 4 inch plates were used, the results were different ; 

 with one electrometer 02 cubic inches of gas were procured, with 2 

 only 14*6 cubic inches. These results depend upon the same circum- 

 stances of retardation as have been already mentioned. 

 (To be continued.) 



II. — The American Journal of Science and Arts, Jar July, 



August, ""it September, \x'-\->. 



Is -March last, Dr. Silliman, the editor of this journal, since its com- 

 mencement, 17 years ago, made an open appeal to his countrymen ill 



