420 Miscellaneous Intelligence. 



nitrous gas. Muriatic acid dissolved it when heat was applied, 

 and the solution remained clear on cooling ; by dilution, a fine 

 white powder was deposited. 



Potash, with heat, dissolved it, and rendered the solution turbid, 

 but did not cause any deposition in 24 hours. — Annates de Chimie, 

 xli. 323. 



26. To ascertain the Admixture of Sulphate of Copper in Bread. 

 — In the Observateur de Liege, MM. Meylinck and Hensmans have 

 given three processes for ascertaining the presence of this salt in 

 bread — the humid way — the dry humid — and the dry. The dry 

 humid, which they prefer, consists in letting fall a drop of ferro- 

 prussiate of potassa on a slice of bread ; whether or not there is sul- 

 phate of copper in the bread, a reddish spot will be formed if the 

 bread be fresh : a blue one, if the bread be sour. Immerse the 

 bread in lime-water, the spot will scarcely change colour, or will 

 become yellow if there be no adulteration ; but, on the contrary, will 

 assume a greenish tint if it contain sulphate of copper. In the second 

 case, expose the bread to the action of ammoniacal gas, which will 

 immediately change the blue colour of the spot to a pale citron 

 yellow if the bread is pure; on the contrary, if it be adulterated, 

 the spot first becomes red, then yellow, and from the yellow it may 

 be brought back to the red, by volatilizing the ammonia, or exposing 

 it to muriatic vapour. By the humid way, we may proceed 

 either, i. By treating the bread with acidulated water, passing the 

 liquor through a flannel, and then examining it by the ordinary 

 re-agents after having neutralized it by ammonia; or ii. By treating 

 the bread with concentrated alcohol, boiling ; the alcohol takes up 

 the salt of copper, and a solution is thus obtained, which is to be 

 treated with the ferro-prussiate. The dry way consists in burning 

 the bread in an unvarnished earthen vessel. A stratum of different 

 coloured ashes is thus obtained, covered with an efflorescence of a 

 mixed green and blue colour. According to M. H. it is preferable 

 to treat separately the ashes and the efflorescence; but Dr. Jacque- 

 mys, of Liege, regards this as useless, because the copper contained 

 in the whole mass may easily be dissolved in nitric acid. The 

 solution having been effected, it is to be neutralized by ammonia, 

 and enough ammonia added to precipitate the alumina from the 

 flour and dissolved by the acid. The presence of copper may thus 

 be ascertained by the hydroferro-cyanate of potass. To determine 

 the quantity of salt contained in the bread, it is necessary, after 

 having precipitated the alumine, to filter the liquid ; add to it prus- 

 siate of potass and of iron, then dry and weigh the precipitate, and 

 from this datum calculate the quantity of sulphate of copper. 



27. — Letter from Sig. Carlo Matteucci of Forli to Professor 

 Gazzeri : — 



" Sir, — The importance of the new fact, in solar electricity, 



