Section of Chemistry and Electricity. 401 



been analysed by Liebig, and subsequently by Dr. Apjohn *, is easily 

 prepared by mixing, in the proportion of atom and atom, the iodide 

 of potassium and bicyanide of mercury, each dissolved in a small 

 quantity of hot water. After a short time silvery scales (resem- 

 bling acetate of mercury) are formed, which constitute the salt in 

 question. The circumstance of this salt being decomposed by all 

 the ordinary acids, would appear to show that it is not capable of 

 demonstrating the presence of muriatic acid in particular ; but as 

 the only other impurities likely to be present in the hydrocyanic 

 acid are sulphuric and tartaric acids, if the appropriate tests of 

 these latter do not indicate their existence, then the formation of 

 biniodide of mercury on the addition of a crystalline scale, or solu- 

 tion of the double-salt above mentioned, may be considered as fur- 

 nishing conclusive evidence of the presence of muriatic acid. It 

 may be also stated, that the only hydrocyanic acid likely to con- 

 tain sulphuric — that prepared from the ferrocyanide of potassium — 

 can be generally recognised, as to the source from whence derived, 

 by its possessing a slight bluish or bluish green tinge, which is 

 quite distinctive. The mode of detecting the presence of muriatic 

 acid above detailed has the advantage over those usually em- 

 ployed, of being very readily applied, and the formation of the re- 

 agent is perfectly simple; it is capable of detecting 1 -4500th part 

 of the acid: if no change of colour ensue on the addition of the 

 salt, we may conclude that the specimen of hydrocyanic acid con- 

 tains no impurity which can interfere with the subsequent estima- 

 tion of its strength. This method, however, is inapplicable to the 

 alcoholized acid of Germany, as the biniodide is soluble in spirit, 

 yielding a colourless solution. If the presence of muriatic acid 

 have been ascertained, its neutralization can be readily effected by 

 the addition of successive small portions of precipitated carbonate 

 of lime, as long as any is dissolved; when free, muriatic acid has 

 been got rid of, and not till then can the estimate of the strength 

 of the specimen under examination be proceeded in with any hope 

 of a correct result. The method of Dr. Ure for effecting this lat- 

 ter end is sufficiently correct for ordinary purposes, if we substi- 

 tute for the red precipitate which he employs, pure peroxide of 

 mercury ; as, independent of the presence of minium and other im- 

 purities, red precipitate is seldom, if ever, free from pernitrate of 

 mercury : if perfect accuracy be desirable, the best method, and 

 probably as simple a one as that just alluded to, is the formation of 

 cyanide of silver by the addition of the nitrate of that metal. 



On Bleaching certain Varieties of Turf for the Purpose of producing 

 a White Fibre for the manufacture of Paper. By R. Mallet. 



The kind of peat used for this purpose is that which exists im- 

 mediately beneath the vegetable surface of almost every lowland or 

 flat bog in Ireland, and is found existing in a stratum frequently 



* [Dr. Apjohn's paper on this subject was published in Phil. Mag. and 

 Annals, N.S. vol. ix. p. 401. — Edit.] 



Third Series. Vol. 7. No. 41. Nov. 1835. 3 F 



