Chemical Analysis of Tabasheer. 135 



rendered muddy by carbonate of ammonia. It was, there- 

 fore, evaporated to dryness. A greyish matter remained 

 weighing 0-08 grain. This matter being digested m mu- 

 riatic acid, there remained undissolved 0-05 grain of silica. 

 The 0-03 grain dissolved, consisted of a mixture of alumina 

 and lime. 



Thus, the constituents obtained were, 



Moisture, .... 0-487 or 4-87 



Silica, 9-050 „ 90-50 



Potash, 0-110 „ MO 



Peroxide of iron, . . 0-090 „ 0-90 

 Alnmina, .... 0^040 „ _(M0 



9-777 97-77 

 The loss, amounting to 2-23 per cent., was probably the 

 consequence of my employing different portions of the 

 tabasheer in different steps of the analysis. For they were 

 not all exactly the same in appearance. Hence, possibly 

 the proportion of the constituents might vary somewhat in 

 each. But my supply of tabasheer was not sufficiently 

 great to admit of a new analysis upon a large scale. I did 

 not weigh the lime ; but do not think it could exceed 0-1 

 per cent. It is needless to observe, that the preceding 

 analysis accords sufficiently with the experiments of Mr. 

 Smithson and Dr. Turner, and, therefore, serves to confirm 

 them. The tabasheer examined by Smithson, Turner, and 

 myself was from India; that subjected to examination by 

 Fourcroy and Vauquelin was from South America. It re- 

 mains to be seen whether the constitution of the American 

 tabasheer be essentially distinct from the Indian, as would 

 appear from the 30 per cent, of alkali, &c. found in it by 

 Fourcroy and Vauquelin. 



Article VII. 



On Madder, and Madder Dyeing. 



( Concluded from page 56 J 



OF THE MODE OF DYEING COMMON MADDER-RED CLEARER 

 AND PURER. 



1. Washing the madder.— Numerous experiments have 

 proved that the colour is not improved by washing the 



