ON ELECTROLYSIS IN ITS PHYSICAL AND CHEMICAL BEARINGS. 317 



iu two dillerent ways : (a) Solutions which are found to be isohydric when viixed in 

 equal volumes jnuat also be isohydric when they are mixed in other proportions. 



This proved to be the case. Phosphoric acid (223-7) and hydrochloric acid 

 (167-4) were mixed iu the ratios 3:1,2:2, and 1:3; oxalic acid (4-947) and acetic 

 acid (4-837) in the ratios 10: 3, 1 : 1, and 3: 10; tartaric acid (1-566) and hydro- 

 chloric acid (1-757) in the ratios 10:3, 1:1, and 3 : 10 ; acetic acid (12-18) and 

 hydrochloric acid (14-54) in the ratios 10 : 1, 10 : 2, 10 : 4, 10: 7, 1 : 1, 2:3, 1 : 2, 

 1 : 5, and 1 : 10. In no case was there a difference between the observed and calcu- 

 lated conductivities which reached the limit of the error of observation (0-5 p.c), 



(6) Solutions which are isohydric xcith any the same solution must also be 

 isohydric with each other. Otherwise, as is easily seen, we might have three solu- 

 tions, among which a permanent current of water would circulate always in the 

 same direction. I have foimd — 



A. (a) Phosphoric acid (225-6) isohydric with oxalic acid (1397 ± 7-5). 



hydrochloric acid (108-8 ± 10). 



(0) Oxalic acid (141-7) 



(a) Hydrochloric acid (88-59) 



(/8) Tartaric acid (75-39) 

 , (a) Formic acid (5-576) 



(/3) Oxalic acid (4-915 ±0 17) 



(166-4). 

 B. (a) Hydrochloric acid (88-59) „ „ tartaric acid (7500 ± 2-5). 



oxalic acid (85-07 ± 35). 

 „ „ (82-08 ± 3-3). 

 „ „ (4-901). 

 hydrochloric acid (5-309). 



„ (5-336 ±0-13). 



It will be seen that the numbers are perfectly satisfactory. 



7. Table of isohydric solutions. — In the following table particulars of isohydric 

 solutions of six acids, as different as possible, are collected ; their conductivities 

 (multiplied by 10") are given, together with the possible errors. Above the con- 

 ductivities I have put in brackets the number of gramme-molecules per litre of the 

 corresponding solutions. These are calculated from Ostwald's numbers. Solutions 

 more concentrated than normal ones have not been investigated. 



8. Since obviously any solution of two acids in the same water can always be 

 represented as two isohydric solutions, it follows that ivhen two acid solutions are 

 mixed the tiuo acids divide themselves tvith reference to the water, so that two 

 isohydric solutions are fm-med. 



From the above table it follows that the specific conductivities of isohydric 

 solutions are approximately equal. 



