Colorado Paper - Progress of Metallurgical Science in the West (6d84f7c4-7b6b-450b-a605-492caebbd979)

H. M. Howe, Boston, Mass. (Communication to the Secretary): One by one our venerated idols are shattered, our cherished beliefs are filched away. Mr. Pearce's interesting experiments on the effect of an intermixture of coal in expelling arsenic from roasting copper-ores seems at the first blush to spike one of the great cannons of our faith. Plattner, however, is so positive that coal does lead to the expulsion of arsenic that we may well pause before accepting Mr. Pearce's results as final, and ask whether there is not some explanation of the discrepancy between them and Plattner's statements. Plattner states that while ferric arseniate decomposes easily under the action of carbonaceous matter with expulsion of arsenic as arsenious oxide (As2O3) and sub-oxide of arsenic (it is now generally thought, I believe, that this supposed sub-oxide is really but a mixture of metallic arsenic and arsenious oxide); cupric arseniate, on the other hand, undergoes this decomposition with difficulty, usually forming a certain proportion of arsenide of copper. Now, may not the whole matter lie just here? Mr. Pearce experimented on an ore containing its arsenic as enargite, sulph-arsenide of copper. This, in roasting, would probably give rise to arseniate