Prof. Del Rio's Analysis of two new Mineral Substances, 113 



f denoting an arbitrary function. It will be easily seen that 



instead of/ x * y , any arbitrary function of y ~7% or of rjT^-p 



may be taken. 



[To be continued.] 



XVII. Analysis of two new Mineral Substances, consisting of 

 Bi-seleniuret of Zinc and Sulphuret of Mercury, found at 

 Cidebras in Mexico. By Professor Del Rio*. 



Tj^ACH step of the traveller in this Republic discovers to 

 -" him something new. Mr. Joseph Manuel Herrera, in an 

 excursion to Culebras, near the mining district of El Doctor, 

 found a mineral resembling cinnabar, accompanied by metallic 

 quicksilver, in the limestone which overlies the red sandstone 

 (arenisca rosea), and he gave me a few small specimens of this 

 substance. Some considerable time afterwards Col. Robinson 

 gave me an additional quantity, informing me at the same 

 time that Dr. Magos had obtained two ounces and a half of 

 quicksilver from sixteen ounces of the ore. 



Under the blowpipe the red ore burns with a beautiful 

 violet-coloured flame, accompanied by much smoke of a most 

 offensive smell, resembling that of rotten cabbage : the resi- 

 due is a grayish-white earthy matter. 



Intimately admixed with the red mineral is another sub- 

 stance so strongly resembling light gray silver ore, that I ac- 

 knowledge that I mistook it, at first, for this ore of silver. 

 My only doubt on the subject arose from the consideration 

 that gray silver ore and cinnabar are never found together. 

 It differs, however, from gray silver in yielding a blacker pow- 

 der when scraped, and which stains more than the powder of 

 the latter. Under the blowpipe nearly the same phaenomena 

 are observed as when the red mineral is submitted to the same 

 test. According to Mr. Chovell, the specific gravity of the 

 gray substance is 5'56, after having been carefully cleared by 

 washing from the calcareous spar of the matrix. That of the 

 red substance, after having also been carefully separated from 

 the spar, is S^; while the specific gravity of hepatic mercury 

 exceeds 5*8. 



The analysis of these minerals is very easy where great pre- 

 cision is not required. Nothing more is necessary than to 

 put fifty grains of the ore in a small retort on the fire ; mer- 

 cury, selenium, and a small quantity of sulphur are imme- 



* Communicated by A. F. Mornay, Esq. 

 New Series. Vol.4. No. 20. Aug. 1828. Q diately 



