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POPULAR SCIENCE REVIEW. 
of salireton was far less than when saligenin is heated with glycerin or 
methylal. In any case the s alicylaldehy de, like the glycerin, plays the 
part only of a liquid of suspension. The salireton melts at 121° # 5, gives off 
gas at 140° as well as the odour of salicylaldehyde, while a black resinous 
residue remains. An examination of this residue showed it not impossible 
that this contained saliretin C 7 H 8 0 (?). For the formation of the latter 
body the following reaction may perhaps take place : 
C 14 H 12 o 3 - c 7 h 6 0 2 = C 7 II 6 0 
Salireton. Salicylaldehyde. Saliretin. 
Recognition of Mercury. — Jiiptner employs the iodide Hg I 2 , which, as is 
well known, is dimorphous, occurring in yellow rhombic crystals as well as 
scarlet square octohedra ( Oest . Zeitung, 1880, xxviii. 92). The latter modifi- 
cation, in which mercury is obtained in the wet way, as well as by touching 
the yellow body produced by sublimation, possesses the property of appearing 
quite white in the light of the sodium flame. The author studied the ap- 
pearance of various colours under such conditions, and examined a series of 
yellow, red, green, and blue colours by the light of sodium and lithium, and 
found that none of them were affected in the same manner as by mercury bin- 
iodide. It forms a means by which mercury can be recognized with certainty. 
Production of Alcohol by an Electric Current. — Berthelot’s experiment 
was recently conducted in the following manner : A battery of eight Bunsen 
elements was connected with an oscillating conmmutator, so that from twelve 
to fifteen currents were sent in alternate directions per second, which were con- 
ducted to two electrodes of spongy platinum. The platinum cylinder was placed 
in acidulated water, and the contact-action so arranged that neither oxygen nor 
hydrogen were given off, but the decomposed water regenerated as rapidly as it 
had been split up. When all had thus been arranged, the two electrodes of the 
apparatus were immersed in a watery solution of glucose. In this way alcohol 
was obtained, although it is true in but small quantity. It is hoped, however, 
by modifying the apparatus that the process may be improved and even made 
of technical importance. — ( Chem . Central Platt., 1880, 288.) 
Remarkable Behaviour of Tin Chloride and Potassium Chlorate. — According 
to Bottger {Polytechn. Notizblatt, xxxv. 96), when two parts by weight of tin 
chloride and one of potassium chlorate are rubbed together (they must previ- 
ously have been rubbed fine in a porcelain mortar) the mass becomes strongly 
heated in a few seconds ; chlorous acid and a large quantity of vapour of 
water are given off. The residue is a yellowish-white mass which dissolves 
in boiling water, and, on cooling, gives splendid brilliant mica-like crystals of 
potassium perchlorate, the supernatant opalescent, milk-like liquid containing 
the oxychloride in solution. 
The Tannic Acid of Oak Bark. — C. Etti prepared the acid from the pro- 
duct of extracting oak-bark with alcohol by digesting it with acetic ether, 
in which it is soluble. He obtained a reddish-white amorphous powder, the 
analysis of which led to the formula C 17 H 16 0 9 as that of the body. From 
it, by heating it to 140°, or by boiling its aqueous solution with dilute acids, 
three anhydrides were obtained. The first anhydride is C 34 H 30 0 17 , the 
second is 0 16 , and the third anhydride C 34 H 26 0 15 : the first is iden- 
tical with the natural phlobaphen of oak-bark, the third with Oser’s 1 oak- 
