Chemistry and Physics. 75 



cyanide, manganese dioxide and acetic acid, and slightly warm- 

 ing the mixture. Acetates of copper and of manganese are formed 

 and the cyanogen is evolved. When the operation is terminated, 

 the addition of sulphuric acid enables the acetic acid to be dis- 

 tilled off for a new operation. In separating the cyanogen which 

 is evolved, from any other gaseous substances with which it may 

 be mixed, Jacqueminfinds that this gas is very readily absorbed 

 by aniline to form cyaniline, and hence recommends this sub- 

 stance as the best with which to absorb it, since neither C0 2 , CO, 

 nor air are appreciably absorbed by aniline. — C. is?.,c, 1005, 1006, 

 April, 1885. a f. b. 



3. On two new AXkalimetric Indicators. — Ville and Engel 

 have proposed two new indicators for alkalimetry, both of which 

 are unaffected by carbonates ; so that by means of these, the free 

 bases may be determined volumetrically in presence of the alkali 

 carbonates. The first of these is sulphindigotic acid. It is pre- 

 pared by neutralizing with calcium carbonate the ordinary solu- 

 tion of indigo in fuming sulphuric acid, diluting with ten parts of 

 water and filtering. While carbonates are without action upon 

 the blue color of this liquid, caustic alkalies change it to yellow . 

 In titering with it, a few drops of this blue liquid are added to 

 the solution containing the caustic alkali, which turns it yellow. 

 As soon as the neutralization is complete, the color of the liquid 

 changes back to blue, passing through an intermediate green. 

 By placing the beaker on a white paper each drop of acid as it 

 enters produces a blue spot at the point of contact, which ceases 

 on neutralization. The second substance proposed as an indi- 

 cator is the soluble blue C. 4. B. of Poirier. This in solution 

 in water (2 parts in 1000) is even more sensitive than the sulphin- 

 digotic acid. In presence of alkali carbonates this solution re- 

 mains blue but becomes red under the influence of the free bases. 

 If to a solution containing both carbonates and free bases, a few 

 drops be added, a rose-red liquid is obtained in which each drop 

 of the graduated sulphuric acid, as it enters, produces a blue 

 color, which so long as neutralization is incomplete is transient, 

 but which as neutralization is approached passes through violet 

 into a permanent blue when no more caustic alkali is present. 

 With these indicators, the determination of free alkali in presence 

 of carbonated, is rendered as rapid and accurate as is ordinary 

 alkalimetry with litmus or orange No. 3. — C. JR., c, 1073, April 

 1885. g. p. b. 



4. On the Separation of Nickel and Cobalt. — Ilinski and v. 

 Knoree have proposed a new method of separating nickel and 

 cobalt founded on the properties of the compounds which these 

 metals form with nitroso-/2-naphthol. If to a neutral aqueous 

 solution of sodium-nitroso-/2-naphthol an excess of a cobalt salt 

 be added in solution, a brownish red precipitate of cobalto-nitroso- 

 /?-naphthol [C 10 H 6 O(NO)] 2 Co is produced which is very sparingly 

 soluble in water. By digestion with potassium hydrate, this pre- 

 cipitate loses slowly, by warming with acids rapidly, a portion of 



