of Edinburgh, Session 1874-75. 
545 
4. Note on the Electrical Conductivity of Saline Solutions. 
By J. G. MacGregor, M.A., B.Sc. Communicated by 
Professor Tait. 
In the Sitzungsberichte of the Munich Academy,* Professor Beetz 
has recently published a review of a paper by Mr J. A. Ewing and 
myself on “The Electrical Conductivity of certain Saline Solu- 
tions,” which was read before the Royal Society of Edinburgh 
during the session of 1872-73, and is published in their Transac- 
tions.! I take the earliest opportunity of discussing the strength 
of the arguments on which his criticisms are based. Unfortunately, 
on account of Mr Ewing’s being at present in South America, I am 
unable to communicate with him. I alone am therefore responsible 
for the contents of the present paper. 
Professor Beetz begins by characterising the short reference 
which we made to his valuable work on the conductivity of solu- 
tions of zincic sulphate J as a “ complete series of mistakes.” “ My 
only precaution,” he writes, “ against polarisation consisted, then, 
in the use of amalgamated zinc electrodes ! Whoever has read and 
understood my paper, must know that the plan of my work went 
beyond the experiments with zincic sulphate solutions, that it 
rather consisted in finding, by a damping method, the conduc- 
tivity of electrolytes generally, relatively to that of a single one.” 
We are accused of having underrated his precautions against 
polarisation and of being ignorant of the scope of his work. There 
were two things which Professor Beetz set himself to accomplish — 
(1.) to investigate absolutely the conductivity of zincic sulphate 
solutions ; and (2.) to determine relatively to it that of other elec- 
trolytes. The first part he has carried out, and his researches in 
this field are generally regarded as authoritative. The second 
part, however, he has not carried out. He made use of two 
original and very ingenious methods for the purpose, but both 
failed. Of one he says himself, “ Es gelang aber nicht brauchbare 
Ausschlage zu bekommen § and of the other, “ Auch diese Methode 
hat mir noch keine Besultate geliefert .” || Now, however one may 
* Sitzungsberichte der Miinchener Akademie, 6. Februar, 1875, pp. 59-70. 
f Trans. Roy. Soc. Edin., vol. xxvii. part 1, 1872-73, pp. 51-70. 
X Poggendorff’s Annalen, cxvii. 1862, pp. 1-27. 
§ Ibid, cxvii. p. 26. || Ibid, p. 27. 
