152 Mr. L. Hunton on the definite Combinations 



to retard the progress of the electrolytic agent. A trough 

 which has been in action and consumed the whole of the fluid in 

 its cells, so as to have its plates covered with flocculent preci- 

 pitated copper, when emptied and again filled with the metallic 

 solution, soon again comes into action, and the electrolytic 

 action is the same, or nearly so, as at first. When the plates 

 are allowed to dry, and are in that state put into the trough 

 with the metallic solution, though there is at first no action, 

 yet it begins in the course of a short time, and goes on effect- 

 ing the electrolyzation of the electrolyte as before. 



Though the trough acts in this way, it is better to wash off 

 the precipitated copper, because the whole surface of the metal 

 is thus exposed ; whereas when not washed off, unequal sur- 

 faces are exposed in the different plates, from part of the pre- 

 cipitate above being carried off when the trough is emptied, 

 and thus the action may not be the same in all the cells. 

 When iron is used, the plates after being washed ought to be 

 dried, before being set aside, because otherwise they become 

 covered with rust, which retards the action. 



As it is of the utmost consequence to avoid as much as 

 possible expense in the fitting up of the trough, I have been 

 led to adopt a modification of that in common use, which is 

 easily renewed with little expense. Instead of using the plates 

 soldered together, the copper plates are fixed into the sides 

 of the trough, thus forming the partitions, on each of which 

 is suspended an iron or zinc plate, by bending the upper ex- 

 tremity, so as to form a sort of hook. This trough acts as 

 powerfully as the others in common use, and it has this ad- 

 vantage, that the iron or zinc plates are easily removed, and 

 cleaned, when required, and are, when destroyed, easily re- 

 placed by others. It is necessary to dry the plates after being 

 washed, to prevent oxidation at the upper extremity, by which 

 the metallic contact would be rendered imperfect. 



XVIII. On the definite Combinations of Sugar with the Jlkalies 

 and Metallic Oxides. By Louis Hunton, Esq., F.G.S.* 



\^7TIEN lime is added to a solution of sugar it is dissolved 

 " in considerable quantity. Dr. Ure in the last edition of 

 his Dictionary says : " Sugar dissolved in water at the tempe- 

 rature of 50° is capable of dissolving half its weight of lime." 

 This 1 believe will be found too large a proportion, for after 

 repeated trials I find its composition the same for every tem- 

 perature between 50° and 130° at which the solution is made 



« Communicated by the Author. 



