154 Intelligence and Miscellaneous Articles. 



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shining in the streak, and its hardness is a little inferior to that of 

 alum. Its specific gravity is 2*039. It is slowly soluble in water, 

 and does not, therefore, possess so powerful an astringent taste as 

 common sulphate of iron. The crystals are not above two lines in 

 length, and are usually aggregated in reniform and botryoidal shapes, 

 consisting of globules with a crystalline surface ; the trivial name al- 

 ludes to the tendency of the salt to produce such imitative shapes. 



When exposed to a moist atmosphere, it becomes covered with a 

 dirty yellowish powder, but remains unchanged in a dry atmosphere : 

 before the blowpipe it intumesces, and gives off water in a glass tube, 

 eaving a reddish yellow earth behind, which according to the flame 

 employed may be changed into protoxide or peroxide of iron. With 

 salt of phosphorus it yields a red glass, which loses its colour on cool- 

 ing. Boiling water dissolves part of it, leaving a yellow ochre, which 

 therefore is an integral portion of the mixture. The solution, nitric 

 acid being added to it, may be precipitated by muriate of barytes, 

 but not by nitrate of silver. Ammonia, with which the salt is digested 

 in a stoppered bottle, takes away all the acid, and leaves the iron in 

 the shape of a slightly greenish black powder. The iron therefore is 

 contained in the salt, not as a pure oxide, but as a compound of the 

 protoxide and peroxide, which is black when pure, and produces red 

 solutions. 



The following are the results of three analyses : 



I. II. III. 



Persulphate of iron, with excess of base, 677 6*85 *) 

 Bisulphate of the protoxide and perox- > 48*3 



ideofiron 35'85 39'92j 



Sulphate of magnesia 26-88 1 7' 1 20*8 



Sulphate of lime 222 671 0-0 



Water and loss 28'28 31-42 30-9 



The second analysis is most correct as to the water. Berzelius con- 

 siders all the substances mixed with salt of iron as foreign to the salt, 

 and uncombined with it. 



ERINITE, A NEW MINERAL SPECIES. 



This substance is arseniate of copper, contained- in Mr. Allan's 

 cabinet. Mr. Haidinger makes the following observations on it. 

 " Though not presenting determinable crystals, the appearance of 

 the specimens in Mr. Allan's cabinet, the only ones which I re- 

 member to have ever met with, are highly crystalline. The indivi- 

 duals are arranged in concentric coats with rough surfaces, produced 

 by the termination of exceedingly small crystals, the layers often not 

 firmly cohering, so that they may be easily separated from each other. 

 These layers themselves are very compact -, they show an uneven, or 

 sometimes imperfect conchoidal fracture, and traces of cleavage. The 

 cleavage probably takes place parallel to the broad faces of rectangu- 

 lar four-sided plates, into which the individual terminates. I have, 

 in several instances, observed something like them by means of a 

 compound microscope, but always very indistinctly. These plates 

 form crest-like aggregations. A circumstance which greatly increases 

 the difficulty of observing the regular forms, is the complete absence 



of 



