Examined by 

 CrelJ. 



375 ANALYSIS OF THE CHINESE RICE-STONE. 



Crcll subjected the rice-stone to several chemical experi- 

 ments in 1781, to find whether it contained rice or its mu- 

 cilage. He exposed some pieces to a strong red heat in a 

 small crucible, but found no indication of any volatile 

 matter, animal or vegetable. The pieces were agglu- 

 tinated together, and adhered to the bottom of the retort : 

 and the substance still retained its colour and semitrans- 

 parency, as before the experiment, and had undergone no 

 loss. 

 Analysed. As no farther experiments on the component parts of the 



rice-stone have been published, its nature has still remained 

 unknown. I have attempted an analysis of it on a very 

 small quantity ; and though this analysis is not very exact, 

 it is sufficient to throw some light on the composition of 

 the stone. The portion analysed was taken from a vessel 

 with two handles, weighing 12 ounces. From its external 

 appearance it might be taken for a greenish gray chalcedony, 

 as well on account of its polish and transparency as of its 

 colour: but the sound it emitted when struck, and still 

 more its specific gravity, which was above double that of 

 chalcedony, since it was 5*3936, showed unquestionably, 

 that it was not this stone. 



It is easily attacked by the file. It breaks easily, with a 

 conchoid fracture, and glassy lustre. In a small spoon 

 before the blowpipe it readily fuses into a small bead ; but 

 on a piece of charcoal this bead is covered with a leaden 

 gray pellicle. Borax and the phosphoric salts difficultly 

 combine with it : but if it be fused in the small platina spoon 

 with carbonate of soda, immediately small globules of me- 

 tallic lead appear. Acids do not act on this stone; 

 accordingly I attacked it by alkalis in the following manner. 

 si j eX( a. One hundred grains of this stone reduced to an im- 



palpable powder were heated red hot with potash. The 

 mixture became hard, and acquired an ashen gray colour. 

 On supersaturating it with nitric acid silex was separated to, 

 the weight of 39 grains. 

 Oxide oflead. &• Sulphate of soda being added to the solution, sulphate 

 of lead was precipitated, weighing 55 grains, which indicate 

 41 grains of oxide of lead. 



c. The 



Specific gravity 

 of a specimen. 



Hardness. 



Treated before 

 the blow -pipe 



