52 Proceedings of the Royal Irish Academy. 



V. — Eepoets from the Chemical Labokatoky of Trinity College,. 

 Dublin. By J. Ejiekson Reynolds, M. D., Prof essor of Chemistry,. 

 University of Dublin. 



IS'o. 2. — On the Composition of Lievhite, as dexeemined by Me.. 

 Eakly's method. 



[Eead, January 22, 1877. J 



Op the several methods which have been devised for the analysis of 

 ferroso-ferric silicates, that which has been published by Mr. WilKam 

 Early, ^ Demonstrator of Chemistry in this laboratory, is probably the 

 most easily managed. The advantages attending its use are chiefly 

 felt in analyzing silicates, which are either insoluble in, or attacked 

 with difficulty by, the ordinary acids ; but it can also be used with 

 great convenience in the analysis of silicate easily acted upon by 

 acids. 



Lie\T.ite is a silicate belonging to the latter class ; and as the 

 formula of the mineral is by no means definitely fixed, I requested 

 Mr. Early to analyze by his method a portion of a particularly fine 

 crystal which I obtained some time ago from the well-known Elba 

 locality, our chief aim being to determine with precision the relative 

 amounts to ferrous and ferric compounds present in the specimen. 

 The analysis was conducted in the following manner : — 

 1-54 grm. of the finely and recently powdered mineral was 

 mixed with 20 cubic centims. of hydrofluoric acid (containing 20 per 

 cent, of real acid) ; and the mixture was boiled for five minutes in a 

 deep platinum crucible with a rather loosely fitting cover. 10 cubic 

 centims., of diluted sulphuric acid (1 part to 2 of water) were then 

 added, 'Sncl the boiling continued for a few minutes. The contents of 

 the crucible were then washed into a flask with air-free water, and 

 the amount of iron in the ferrous condition determined as rapidly as 

 possibly by standarclpotassic permanganate solution. Another quan- 

 tity ;. of the mineral was acted upon by strong hydrochloric acid; 

 perfect decompositioij. was effected, and a gelatinous mass formed; the 

 product was evaporated to dryness, and the silica separated in the 

 usual way. The acid filtrate from the insoluble silica was then 

 saturated with chlorine gas, and ammonia afterwards added in 

 slight excess ; the mixture produced was then boiled in a closely 

 covered beaker in order to remove the excess of ammonia, the solu- 

 tion rapidly filtered, and the precipitate collected and ignited with 

 the usual precautions and weighed. The product contained all the 

 iron as ferric oxide, the alumina, the manganese as Mus O4, and a 

 trace of silica. The silica was separated from this mixture by 

 hydrochloric acid ; and the filtrate was subjected to the double 



1 " Chemical News" for October 9th, 1874. 



