288 Intelligence and Miscellaneous Articles. 



the result that isohydi-ic solutions contain equal dissociated parts 

 per unit of volume. The author couipares this theoretical conclu- 

 sion with the results of his determinations of isohydric solutions, 

 and finds a satisfactory agreement in the twenty-two cases which 

 can be calculated. The author deduces further in the same way 

 the general properties of isohydric solutions as found experi- 

 mentally. 



If to a solution of an electrolyte, a second electrolyte is added 

 which has one ion common with the first, the state of equilibrium 

 between the non-dissociated and the dissociated parts (the ions) of 

 the first electrolyte is displaced, and so that the dissociation is 

 less. This is particularly remarkable when the first electrolyte is a 

 feeble acid or base. As moreover, according to the author, the 

 facility with which a body reacts is proportional to the dissociated 

 portion, then from the general conditions of equilibrium the in- 

 fluence of extraneous electrolytes on the velocity of reaction may 

 be calculated. Such a calculation has been made for the case for- 

 merly investigated experimentally by the author, the saponification 

 of ethyle acetate by ammonia, and yields results which agree with 

 experiment. The author concludes from this calculation, that all 

 ammonia salts act in this case in the same manner, as has been 

 found. Other regularities observed in saponification may be de- 

 duced in the same way. 



The author proves in conclusion, that if quantities a, h, c, d of 

 four isohydric solutions of electrolytes, I^Jj, I^J^, I2J^, and I.^J^, are 

 mixed with each other, there can be no chemical change between 

 these four bodies, provided only a . d=^h . c. A similar conclusion 

 can be drawn for any given number of electrolytes. The chemical 

 equilibrium between several electrolytes in the same solution may 

 consequently be calculated from these regularities. — Zeitschrift fur 

 Phys. Ohem. p. 284 (1888) ; BeiUdtter der PJiysih, vol. xii. p. 678 

 (1888). 



ON AN ELECTEOCHEMICAL ACTINOMETER. 

 BY MM. GOUY AND RIGOLLOT. 



Two copper plates, one of which was heated in a Bunsen's flame 

 nntil the iridescent colours disappeared and the plate had become 

 of a homogeneous brown, while the other is bright, or both are 

 oxidized, are immersed in solution of sodium chloride. When 

 light falls on an oxidized plate it becomes more strongly positive. 

 The action is instantaneous and disappears in darkness : the ap- 

 paratus is sensitive to aU colours. On closing the circuit by a few 

 ohms resistance the alteration of electromotive foi'ce is somewhat 

 greater. Bromides act similarly, iodides somewhat more feebly. 

 When the copper plates are heated too strongly they become less 

 sensitive. They may advantageously be coated on the back with 

 paraffin during cooling. — Comptes Bendus, p. 1470 (1888) ; 

 Beibldtter der Physih, vol. xii. p. 681 (1888). 



