f 4(35 ) 



.1 neio determination of the plait po int, indepetuhitt 

 of the preceding one. 



27. It is now ciisy to obtain sucii a dctermiiiation with tiic aid 

 of (73) aiui (91). Kor in the plaitpoint we have: 

 7^ = ; .«" = xp ; v" = vp . 

 From (73) follows immediately (47); from (91): 



v'p = 2^' -f i [(2/- 3xr-24 (2y'-3x') (y'->c') + lG (3y'-2x')J..> ; . (93) 



from which in connection with (47) we find again (48). 



Physics. — "Some remarkable phenomena, roneernim/ the electric 

 circuit in electrolytes". By Mr. A. H. SiiiKs. (Conimunicated 

 by Prof. H. A. Loüentz). 



On etching of metal-alloys by means of tlie electric cnrrent, as 

 communicated in the proceedings of the meeting of September 27, 

 1902, I met with a great dilliculty. In some cases the hydrogen 

 develoj)ed at the kathode was very troublesome, namely when, instead 

 of escaping inmiediately it divided itself in small bubbles through the 

 liquid and stuck to the object to be etched used as anode. This 

 obstacle was overcome by surrounding the kathode with line bi-ass-gauze, 

 so that the gasbubbles were compelled to escape directly in this case. 

 The gauze was hung up aj)art, consequently there was no contact, 

 whatever, with one of the electrodes. The etching being finished, 

 copper proved to have been precipitated (m the wires of the gauze, 

 which dei)Osit was almost conform to the shape of the electrodes. 



Tills was still more visible at a second etching-experiment with the 

 same co})per-alloy : a small cup was placed under the anode, ^\ili(•ll 

 }>artly hung in it. Again on the gauze a copper-deposit was perceptible, 

 which showed at the lower side a distinctly designed horizontal 

 margin, nearly as high as the brim of the cup. 



It was to be expected, that copper should precipitate on the gauze, 

 placed between the electrodes, as the whole apparatus can be con- 

 sidered as two voltameters, connected in series'). But, why is by this 

 electrolysis not the whole side of the gauze, facing the aiuule, cop- 

 pered, as is the case with the kathode by any ordinary electrolysis? 



To answer this (piestion tiie experiments were altered somewhat. 



1) Tho anode and the side of the gauze facing it, are tlie •'lectrodes of one, 

 the other side of it and the kathode, liiose of the oilier voltameter. 



31 

 Proceedings Royal Acad. Amsterdam, Vol. V. 



