Minerals from Terlingua, Texas. 273 



being effected by sodium hydroxide, and the little mercury 

 that "goes into solution with the chlorine by this operation being 

 recovered. Calculated to gangue-free substance the results 

 were as follows : 



Analyses of eglestonite calculated to gangue-free substance. 





Theory 

 Hg 4 CloO 



I 



0-1195 g. 



At. ratio 



II 



0-1008 g. 



At. ratio 



III 



0-1198 g. 



At. ratio 



Hit... 



90-21 



88-33 



4-11 



88-94 



3-86 



89-73 



3-99 



CI 



7-99 



8-32 



2-18 



8-23 



2-02 



S'12 



2-03 



0.... 



... 1-80 



1-72 



1 



1-84* 



1 



1-80 



1 





100-00 



98-37 



99-01 



99-65 





Iii all cases the mercury is probably low, and calomel was 

 present to a slight extent in sample I at least. It is quite prob- 

 able that the oxygen was less accurately determined than the 

 chlorine, but the effect of low mercury and the presence of cal- 

 omel are better brought out by the ratio based on oxygen than 

 on chlorine as unity. The formula plainly indicated is Hg 4 Cl„0, 

 or J3g 2 0.2HgCl, one that is in full agreement with the quali- 

 tative behavior of the mineral. The variations in the analytical 

 data reported by Moses are so wide that the excellent agree- 

 ment of his averages with the formula Hg 6 Cl 3 2 can be due 

 only to a balancing of large errors. The oxygen values of his 

 table were indirectly determined and are affected by the errors 

 involved in other determinations, which inspection shows were 

 large. 



The ammonium-bromide method, used with kleinite for deter- 

 mining nitrogen, might probably be employed successfully 

 with eglestonite and terlinguaite and any other compounds of 

 similar kind for the indirect but very accurate determination 

 of the basic oxygen in them. 



Two specimens of what was supposed to be eglestonite were 

 analyzed, but with results indicative of a mixture of terlinguaite 

 with calomel, though the appearance of both was decidedly 

 against this. Possibly they represent a new species. 



Calomel. 



The crystals of calomel often reach a large size, some being 

 l-| om in diameter. They are very rich in forms, a total of 30 

 having been observed, of which 10 are new. The crystals are 

 frequently twinned, twinning plane e\ 011 \. The formula for 

 calomel being well established, no chemical work was done on 

 this mineral. 



* 1-90 by loss in wt. of ign. tube. 



