O. A. Derby — Notes on Monazite. 217 



Art. XX.— Notes on Monazite ; by Orville A. Derby. 



Solubility in acids. — In order to test the relative solubility 

 of the mineral in different acids a sample of monazite sand 

 from Prado, Bahia, was freed from all admixture by careful 

 picking and after grinding was submitted in parcels of about 

 half a gram each to the action of 100 centigrams of the ordi- 

 nary laboratory acids each diluted with one part of water. After 

 standing for 68 hours without heating, phosphoric acid was 

 determined in each solution as follows: in nitric acid solution, 

 2*51 per cent ; in hydrochloric acid, l - 62 per cent ; in sul- 

 phuric acid, l - 39 per cent. 



Magnetism. — In cleaning up residues with the electro-mag- 

 net it has been found that monazite can be quite successfully 

 separated from its usual associate, zircon, and that when mona- 

 zite and xenotime occur together the latter can, by a proper 

 graduation of the points, be almost entirely drawn away from 

 the former. In one case in which the instrument had been 

 used with an opening between the points of about a centi- 

 meter, for the separation of pyroxene of the acmite type which 

 may be presumed to carry about 30 per cent of iron oxide, a 

 mixed sample of monazite and zircon was very neatly and 

 quickly separated without reducing the distance between the 

 points, both minerals being equally free from iron staining or 

 inclusions. 



Microchemical reactions — A single granule of the mineral, 

 no matter how minute, can be rapidly and securely identified 

 by moistening it with sulphuric acid on a slip of glass and 

 burning off the acid over a spirit lamp. The characteristic 

 crystallization of cerium in double ball-shaped clusters of radiat- 

 ing needles or minute cucumber seed-shaped isolated crystals, 

 can usually be detected after this operation in the ring of 

 evaporated material about the granule, but better after adding 

 a drop of water and allowing it to evaporate in a desiccator. 

 Another drop of water with a slight admixture of ammonium 

 molybdate solution added to the same preparation gives on 

 evaporation a very satisfactory reaction for phosphoric acid. 

 The reagents are best applied by means of a small loop on the 

 end of a very fine platinum wire and an excess should be 

 avoided, especially with the acid, as too large a drop is liable to 

 run in a very annoying manner in the heating. The same 

 reactions are given by the recently discovered cerium-alumi- 

 nium phosphate, fiorencite of Hussak and Prior, but this can be 

 distinguished by its form and cleavage when these are recog- 

 nizable. The microcrystalline forms of cerium and yttrium 



