Intelligence and Miscellaneous Articles. X&\ 



With this therefore the test solution was prepared, of such a 

 strength, that each division, by measure in the ordinary alkalimeter 

 tube, should be equivalent to the one-tenth or one-fourth of a grain 

 of pure tannin, and thus the number of divisions used would indicate 

 the proportion of available tannin or substance precipitable by ge- 

 latin contained in any specimen. A given weight of the sample 

 under trial was then infused in water, or if necessary the astringent 

 matter extracted by boiling, and the clear liquid precipitated by 

 the test solution until no further deposit occurred. 



It was necessary in the course of this operation to test at intervals 

 a portion of the solution under examination, to ascertain the pro- 

 gress of the trial ; and this, from the nature of the precipitate, was 

 attended at first with some little difficulty : paper filters were inad- 

 missible from the quantity of the solution they would absorb, and 

 thus introduce a source of extensive error ; subsidence rendered the 

 operation very tedious. The plan I have adopted is as follows : — a 

 piece of glass tubing, about twelve inches in length and about half 

 an inch internal diameter, is selected, and this has a small piece of 

 wet sponge loosely introduced into its lower extremity, and when 

 it is wished to abstract a part of the fluid under investigation for a 

 separate testing, this is immersed a few seconds in the partially pre- 

 cipitated solution ; the clear liquid then filters by ascent through the 

 sponge into the tube, and is to be decanted from its other extremity 

 into a test glass ; if on adding a drop of the gelatin solution to 

 this a fresh precipitate is caused, the whole is returned to the ori- 

 ginal bulk, and the process proceeded in, and so on until the opera- 

 tion is perfected ; this method of operating is facilitated by conduct- 

 ing the examination in a deep glass. After a few trials the mani- 

 pulation will be found extremely easy, and in this way considerable 

 accuracy may be arrived at. — From the Proceedings of the Chemical 

 Society. ________ 



ON THE TWO VARIETIES OF ARSENIOUS ACID. By M. BUSSY. 



The author first gives a new process for determining the quantity 

 of arsenious acid. This process is based on the employment of stand- 

 ard reagents. The reagent which he uses is permanganate of pot- 

 ash, which M. Marguerite has already successfully employed for the 

 quantitative determination of iron. 



When a solution of permanganate of potash is poured into a solu- 

 tion of arsenious acid, it becomes arsenic acid, and the red colour of 

 the reagent disappears. The liquor begins to become coloured only 

 when the transformation of arsenious acid is complete. When, then, 

 a standard solution of permanganate of potash is prepared, the quan- 

 tity of arsenious acid contained in any solution may be determined 

 by that of the permanganate required to convert it into arsenic acid. 



M. Bussy states that the two varieties of arsenious acid, the vi- 

 treous and opake, absorb the same quantit}'' of permanganate, and 

 consequently that the diiFerences observed in their solubility is not 

 derived from any difference of oxidizement. 



With respect to the solubility of the two varieties of arsenious 



