Chemical Science, 221 



jar, over mercury, and oxyp^en p^as p:radually passed in until absorp- 

 tion ceased, and then the liquid coutaininj? the ])recipitated indigo 

 was evaporated to dryness at 212°. The weig'ht of the substance 

 was increased to 0.047, i. e,. 11.5 per cent. 



Not having" obtained indigogene perfectly pure, M. Liebegdid not 

 attempt to analyze it for the ultimate composition. He remarks, 

 that indigo is, perhaps, the only organic body from which one of 

 its constituent parts may be taken without total decomposition ; and 

 which, by oxidation, passes to the state of an indifferent body, having 

 much analogy with peroxides. — A?in. de Chimie, xxxv. 269. 



39. On the mutual Action of Ethers, and other Substances. — From 

 experiments made by M. Henry, he concludes that when metals 

 easily oxidizable, or oxides which unite with acetic acid, are put 

 into sulphuric ether, they produce larger or smaller quantities of 

 acetates, probably, not by decomposing the sulphuric ether, but the 

 acetic ether which is always mixed with it ; and that it is in conse- 

 quence of the saturation of the acetic acid set free from the ether 

 by this decomposition, that sulphuric ether does not redden litmus 

 paper when evaporated, whereas it acts differently when being 

 slightly heated, the quantity of acetic ether contained in it is allowed 

 to decompose by the action of the air. 



Nitric and acetic ethers are described as being easily decom- 

 posed by the action of many bodies without the assistance of heat, 

 if aided by time. Amongst the products of the action are the acids 

 of the ethers, acetates, and alcohol which dissolves the salts formed. 



hur. de Chimie Med. 



40. Faraday's Chemical Manipulation. — The kindness of a 

 friend at Bristol has pointed out to me an error in the directions 

 relative to alkalimetry, which I have given in the above work : this I 

 am desirous of correcting, and, by permission of Mr. Brande, have 

 the opportunity of doing so in the Quarterly Journal of Science. 



The mistake, which arose from using the wrong specific gravity of 

 two that were required in calculation, occurs in the paragraphs 

 (599,600,) but fortunately is prevented from occasioning any expe- 

 rimental error by the directions given in (602). The acid of spe- 

 cific gravity, 1.141, directed to be used, is too strong for the quan- 

 tities marked upon the tube. The substitution of one of specific 

 gravity 1.127, will correct the error, and may be obtained very 

 nearly by mixing 19 parts, by weight, of strong oil of vitriol, with 

 81 parts of water. 



The alterations required may be made in the volume with a pen, 

 as for errors of the press, by reading '* 1.127" for "1.141" in lines 

 25 and 30 of page 276, and lines 2 and 13 of page 277; and 

 *' nineteen* for " one" in line 27, and " eighty-one" lor " four" in 

 line 28 of page 276.— M. F. 



