Chemical Science. 191 



than carbonic acid. It exists in the seeds of the staves-acre. 

 m combination with malic acid, and in company with the fol- 

 lowing- principles:—!. A brown bitter principle precipitable 

 by acetate of lead. 2. Volatile oil. 3. Fixed oil. 4. Albu- 

 men. 5. Animalized matter. 6. Mucus. 7. Saccharine mu- 

 cus. 8. Yellow bitter priciple, not precipitable by the acetate 

 of lead. 9. Mineral salts.— Amiales de Chim. xii. p. 358. 



15. Analysis of Zinc Ores by Mr. Cooper. 

 Dear Sir, %9, Strand, March 16, 1820. 



My friend Mr. L. Potts, of Truro, placed in my hands 

 last summer two minerals, requesting me to undertake an exa- 

 mination of them ; one of which I consider to be the mineral 

 termed Brown Mammillated Blende, and the other I do not 

 recollect to have seen described, unless it be that which is 

 called Silicate of Zinc. I have accordingly analysed them, 

 and find their component parts as stated beneath. The mineral 

 IS of a chocolate brown colour within, but externally of an ash 

 gray; its fracture choncoidal and somewhat shining; streak 

 bright brown. Before the blow-pipe it melts and white vapours 

 are given off, and it becomes black ; if the heat be continued for 

 a sufficient length of time it is nearly dissipated. I find 100 

 parts of it to contain of Zinc, 61.5 



Sulphur, 30.8 



Arsenic, 4.8 



Ox. iron, 1.8 



98.9 

 The other mineral is found as a coating upon quartz in 

 pseudomorphous crystals of a dark gray colour, nearly ap- 

 proaching to black ; the exact form of the crystal I have not 

 been able to determine, but to the best of my judgment they ap- 

 pear to be truncated cubes. When heated before the blow-pipe 

 it decrepitates, and if the heat be urged to great intensity (such 

 as by a mixture of oxygen and hydrogen, or by oxygen through 

 the flame of a spirit lamp,) it melts into an opaque yellow 

 enamel which beconics nearly white on cooling. 100 parts 

 '.'ontain 



