Intelligence and Miscellaneous Articles' 75 



to circumstances, the proto- and perchlorides of iron with excess of 

 arsenite or arseniate of potash. 



Protoarsenite of Iron. — This is immediately precipitated in whitish 

 flocks ; but by washing and the contact of the air, it soon becomes 

 of an ochre-yellow colour. Dried in this state and heated in a tube, 

 it yields water, and afterwards fuses, swells up and produces a white 

 crystalline sublimate of arsenious acid. The fused mass is of a deep 

 rust colour. 



When treated with potash it becomes of a very black colour, 

 which is to be attributed to the black magnetic oxide resulting from 

 the partial oxidizement of the protoxide of iron ; by continued ex- 

 posure to the air while moist, it became of the brown colour of hy- 

 drated peroxide of iron. 



Per arsenite of Iron. — This was of a fine ochre-yellow colour, which 

 did not alter during washing carried on in contact with the air. Dried 

 and heated in a glass tube it swelled up and fused, yielding at first 

 water and afterwards a white sublimate of arsenious acid. When 

 treated with potash the greater portion of it was dissolved ; the solu- 

 tion, as well as the undissolved portion, were of the colour of rust 

 of iron. 



Protoarseniate of Iron. — Recently precipitated it is of a white 

 colour, but becomes bluish-gray by exposure to the air. Dried at a 

 moderate heat and then heated to redness in a tube it fused, yielding 

 water and a white sublimate, which was not crystalline, but destroyed 

 the transparency of the glass ; the fused mass became of a blackish 

 colour. The protoarseniate, which had partly become arseniate of 

 the black oxide of iron, by exposure to the air, was mixed with 

 potash and became immediately of a black colour ; this, by some 

 days' exposure to the air while moist, became of the brown colour 

 of hydrated peroxide of iron. 



Protoarseniate of iron dissolved in cold hydrochloric acid, and 

 treated with a few drops of a solution of chloride of sodium and 

 gold, soon occasioned the production of a considerable quantity of a 

 brown powder, which, when exposed to the heat of the blowpipe, 

 fused into a brilliant globule. 



Perarseniate of Iron was white with a tint of gray ; washed in con- 

 tact with the air its appearance did not alter. After drying at a mode- 

 rate temperature it was heated to redness in a tube, and yielded water 

 without undergoing fusion, and without producing any sublimate. 

 Put into contact with potash it became immediately of a rust-brown 

 colour, without any black tint. — Ann. de Ch. et de Phys., Avril 1844. 



DESCRIPTION AND ANALYSIS OF PENNINE. BY MM. MARIGNAC 

 AND DESCLOIZEAUX. 



This substance, discovered and named by M. Frobel of Zurich, 

 occurs in crystals or large lamellar crystalline masses. 



The primary form is an acute rhomboid of 63° 15'. The very small 

 crystals only possess this form perfectly ; the larger ones are very 

 deeply truncated in a direction perpendicular to the axis, so that they 

 become tables of less or greater thickness, with triangular or hexa- 

 gonal bases, the planes of which are triangles or trapeziums, forming 



