414 Mr. Greville Williams on Emeralds and Beryls. [June 19, 



the carbon determination, but a correction had to be applied to the 

 hydrogen. The necessity for minute precaution will be evident when it 

 is considered that 1 grin, of beryl A, or emerald, only yielded 3 milli- 

 grammes of carbonic anhydride. 



Estimation of Carbon and Hydrogen in Peruvian Emerald and Beryl A. 



I. 0-9725 grm. beryl A gave 0-0030 carbonic anhydride and 0*0131 water. 

 II. 1-0082 „ „ „ 0-0031 „ „ 0-0174 „ 



III. 1-1690 „ emerald „ 0-0030 „ „ 0-0140 „ 



or, per cent. : — 



Beryl A. Lewy's 

 * Emerald. Emerald 



I. II. (mean). 



Carbonic anhydride 0*31 0*31 0-26 28 



Water 135 1-73 1-20 1 89 



In working on such minute quantities, it is not easy to speak with 

 certainty as to the proportion of hydrogen contained in emeralds and 

 beryls which is not due to the water present; and the difficulty is in- 

 creased by the fact, insisted upon by Boussingault*, that these stones do 

 not give off all their water below a red heat. If it be considered per- 

 missible, which I cannot admit, to calculate the hydrogen on the prin- 

 ciple of deducting the water found on ignition in a crucible from that 

 formed during the combustion in oxygen, and then calculating the per- 

 centage of hydrogen on the difference, as Lewy has done, the results 

 would be as follows : — 



Beryl A. Lewy's 

 Emerald. Emerald 



I. II. (mean). 



Carbon 0-08 0-08 0*07 0-08 



Hydrogen 0-06 0-11 0-04 



The smallness of the values obtained, and even the very fact of their 

 close approximation, make me offer them with a certain amount of 

 reserve, and I shall endeavour to repeat them upon much larger quan- 

 tities as soon as I have found a method of avoiding all possible sources 

 of error. 



I have not inserted the numbers given by Boussingault, as there appears 

 to be some mistake in them. He found 0*24 per cent, of carbon in the 

 morallons, and yet says that this number agrees with two of Lewy's 

 determinations, one of which (he says) gave 0*21, and another 0*25 ; 

 whereas I find, on reference to Lewy's memoir, that that chemist ob- 

 tained in the two experiments alluded to 0-21 and 0*25, not of carbon, 

 but carbonic anhydride. 



As it was possible that some of the carbon found in these experiments 

 might have been derived from the steel mortar used hi the prehminary crush- 



* Loc. cit. 



