9$ Mr. D. Forbes's Chemical Examination of, 



The colour varies from a grayish-brown to a rich clove-brown ; 

 streak yellowish-brown j glance resinous to semi-metallic. In 

 small splinters translucent. 



Hardness 6*5, being capable of scratching orthoclase. Brittle. 

 Fractm-e splintery up to subconchoidal. 



Fragments of the crystals heated to i-edness in a tube decre- 

 pitate, and evolve water, becoming at the same time of a fine 

 greenish-yellow colour. Dissolves in borax to a glass, which is 

 brownish-yellow whilst hot, becomes green under cooling, and 

 when cold is greenish-yellow. With microcosm ic salt leaves a 

 residue undissolved, and gives a glass which is yellow whilst hot, 

 and becomes green on cooling. 



The spccitic gravity of a fragment possessing cleavage planes 

 was found to be 5-36 ; another fragment more conchoidal in 

 fracture gave 5-13 ; both specimens being pure. 



The specimen chosen for analysis had the cleavage planes 

 better expressed than usual, and was perfectly free from inter- 

 mixture. When finely powdered it was of a gray-brown colour, 

 and on ignition lost weight, becoming of an umber-yellow colour. 



The powder was decomposed by boiling with concentrated 

 sulphuric acid in a platinum vessel; the columbic acid which 

 remained undissolved being washed and determined, it became 

 of a fine citron-yellow colour on heating, but when cold had 

 recovered its original white colour. 



The solution was rendered alkaline by ammonia, and oxalic 

 acid then added until the solution reacted slightly acid. The 

 precipitated oxalates were collected and ignited, when they ap- 

 peared of a faint v/hitish-yellow colour without a trace of brown, 

 so that probably little or no didymium was present. 



They dissolved readily and completely in hydrochloric acid, and 

 this solution was precipitated by ammonia and filtered ofi'. Lime 

 was determined, as usual, in the filtrate by precipitation as oxa- 

 late. No magnesia was found. 



The precipitate containing only yttria, with the oxides of 

 cerium and lanthanium, was redissolved in a little sulphuric acid 

 and boiled with a concentrated solution of sulphate of potash, 

 thus separating the eerie oxides, which were filtered ofi", dissolved 

 in hydrochloric acid, precipitated by potash, redissolved in hydro- 

 chloric acid, precipitated by ammonia, and determined; they 

 were then converted into* nitrates, ignited, and the lanthanium 

 separated by digestion in a solution of chloride of ammonium 

 and determined. 



The yttria was precipitated from its solution in sulphate of 

 potash by caustic potash, dissolved in hydrochloric acid, repre- 

 cipitated by ammonia and determined. 



The original solution from which the oxalates had been sepa- 



