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



Specific gravity of Emeralds ( Canulillos) before fusion. 



No. of experi- 

 ment. 



w. 



W. 



& 



pi. 



D. 



I. 



4-4964 



2-8293 



o 



16-5 



•998921 



2-69 



n. 



4-4961 



2-8294 



17-0 



•998841 



2-69 



in. 



1-6655 



1-0486 



16-0 



•999002 



2-70 



The formula used was 

 where 



W is the weight in air, 



W the weight in water, 



pt the specific gravity of water at t°, 



t the temperature of the water, 



D the specific gravity. 



One of the above emeralds was exposed for three hours in a platinum 

 crucible to a bright reddish-yellow heat. At the end of the operation it 

 was rendered opaque on the edges, but the green- colour was not destroyed. 

 This experiment completely confirms those of Wohler and Eose and Hof- 

 meister. It is, I think, quite evident that no organic colouring-matter 

 could withstand such a temperature for so long a time. The announce- 

 ment by Lewy that the depth of colour of emeralds is in proportion to 

 the amount of carbon present, made it at first appear improbable that 

 colourless opaque beryls would contain any of that element. The power 

 of the colouring-matter to resist a red heat having, however, made me in- 

 clined to disconnect the question of the colour from that of the presence of 

 carbon, I made experiments to determine whether beryls contained that 

 element, and, if so, to what amount. An experiment was made at this 

 stage of the inquiry (see p. 414), the result of which showed that the beryl 

 analyzed* contained the same amount of carbon as Lewy's emerald. As it 

 was just possible that the small increase in weight of the potash-tubes used 

 by Lewy, Boussingault, and myself, in determining the carbon, might not 

 have been really due to the absorption of carbonic anhydride, but to some 

 volatile inorganic acid produced on heating the emeralds and beryls to 

 redness in an atmosphere of oxygen, I felt it necessary to settle this 

 question definitely. With this intention I burnt 1*2 grm. of beryl A in 

 a platinum boat/ in a current of oxygen. The water produced was re- 

 ceived in a U-tube filled with fragments of asbestos moistened with sul- 

 phuric acid. The carbonic anhydride was received in a Geissler's potash- 



* As this beryl will be repeatedly alluded to in this paper, and especially in the 

 second part, I shall, for convenience of reference, call it " beryl A." It was found in 

 Ireland. 



