1820.] extracted from Pyrites at Fahlun. 27 



Seleniuret of copper has a paler colour than eukairite, and 

 has almost the appearance of native silver. It is soft, may be 

 hammered and polished, and then assumes the colour of tin. 

 Even the black spots of the carbonate of lime assume a metallic 

 polish when filed or rubbed against a hard body. When heated 

 in the requisite vessel, it does not yield selenium. Hence it is a 

 pi'otoseleniuret. 



We have then two species of minerals containing selenium ; 

 both of which in the chemical system of mineralogy belong to 

 the family of copper ; namely, seleniuret of copper = Cu Se, to 

 which I think it superfluous to give any other name than the 

 chemical appellation ; and eukairite = 2 Cu Se + Ag Se^. 



Article IV. 



Ansicer to Mr. Venahles's Queries respecting Cyder-making. 

 By Chemico-Medicus. 



(To Dr. Thomson.) 



SIR, Bollon-row, Piccadilly, Oct. 9, \8\'3. 



The attention I have paid to the making of cyder, and other 

 vinous liquors, in this country, has emboldened me to answer 

 the queries of your correspondent, the Rev. Mr. Venables, rela- 

 tive to fermentation of the juice of the apple. 



To t/ie first Qucri/. — I know of no method of neutralizing the 

 malic acid, except by an alkali, which, of course, would injure 

 the cyder. If the apples which yielded the juice were not ripe, 

 it certainly would be advisable to add to it, previously to ferment- 

 ing it, a quantity of sugar, otherwise the fermented liquor will be 

 so weak that it will soon run into the acetous fermentation. If 

 this addition be not made, a portion of some alcohol, as brandy, 

 rum, or malt spirit, should be added, to keep the cyder in a vinous 

 state. Brandy, I know, is made use of by some cyder-makers, 

 near Ledbury, in Herefordshire, with a view of preventing it 

 passing beyond the vinous stage, or, as they say, to preserve its 

 richness ; and those makers are particularly celebrated for mak- 

 ing superior cyder. The addition of a spirit, after the first stage 

 of fermentation, I consider to have the same effect as that of 

 sugar previous to fermentation ; the advantage of the latter 

 arising from a production of a spirit which preserves the cyder 

 in a vinous state. Another circumstance which powerfully con- 

 tributes to this end is the grinding of the kernels of the apples, 

 as suggested, I think, by Mr. 11. Paine Knight, the peculiar 

 hitter quality of which not only gives the cyder a fine flavour, 

 but very powerfully tends to preserve it in a vinous state. Some 

 months ago I was led to make experiments with the saccharine 



