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POPULAR SCIENCE REVIEW. 
tlie resistance of the arc is proportional to its length, and increases as the 
intensity diminishes. The work performed by the current in the luminous 
arc is proportional to the intensity so long as the electro-motive force of the 
battery remains constant. 
The Electrolysis of Acetic forms the subject of a paper read before 
the French Academy by M. Burgoin. The apparatus he employs is as 
follows : — A tube closed at the upper extremity with a caoutchouc cap, and 
at the lower extremity closed with the exception of a very small hole. 
Through the cap passes a small syphon tube almost capillary, as well as a 
platinum wire, which terminating inside the tube in a plate of that metal, 
forms one electrode. This tube is encircled by a larger one of such capa- 
city, that when the disengaged gas in the interior exerts a pressure of four 
centimetres, the volume of solution in each tube shall be the same. In the 
annular space formed by these tubes the other electrode is plunged. Experi- 
ments were made with a neutral solution of acetate of potash which had 
been analysed : after submitting it for six hours to the electrolysing 
action of four elements, a portion of the liquid was drawn off from the 
neighbourhood of each pole and analysed. The conclusions arrived at are 
that the decomposition into carbonic acid and carburetted hydrogen is 
almost nil, and that the greatest loss is at the positive pole. The results 
of M. Burgoin’s experiment would seem to be : — 1. The current acts 
on acetate of potassium as on a mineral substance. 2. In a moderately 
alkaline solution the oxygen reacts on the elements of the anhydrous 
acid, and gives rise to a normal oxidation, whence results carbonic acid 
and hydride of ethylen : CgHgOg-h 02=20204+04116. 3. A certain 
quantity of acid is totally consumed under the influence of oxygen 
furnished either by the salt or by the alkaline water. 4. The two poles 
suffer unequal losses. Almost the whole of the salt which disappears 
belongs to the positive pole. 5. The current acts on the free acetic acid in 
the same manner as sulphuric acid ; it concentrates the acid at the positive 
pole. — Vide Comptes Rendus, tom. Ixv. No. 24. 
A Metallurgical Spectroscope. — The application of the spectroscope to 
metallurgical processes has not been confined to England. Professor Osborn, 
in a letter to the Scientijic American, gives the following account of an 
instrument devised by him for this purpose, and of his observation with its 
acid: — ^^The instrument complete is so arranged that the observer reads 
the degree on the scale by the actual light which be is analysing. The very 
light which comprises, in its flame, the vaporised metal, as lime, iron, 
chromium, titanium, sodium, &c., discloses to the observer in the spectral 
form, not only its own nature, but often to a great degree, the approximate 
quantities found in the original ore or even in the coal used, or from the 
wasting brick of the furnace. Nothing can exceed the beauty of the 
spectral forms which suddenly appear and disappear in the otherwise 
darkened tube, as the observer stands at the ^ tunnel head ’ of the furnace, 
watching, as it were, the spectral secrets of that terrible flame which pours 
forth from the stack, especially when, after the ^ cast ’ and consequent cessa- 
tion of the blast, that blast is again turned on. The bright yellow bar of 
sodium is almost always present during examination of all flames resulting 
from the use of any and all forms of anthracite in the furnace and forge, or 
