Elements of the Art of Assaying Metals (Paperback)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: Of C E M E N T S. 152. We have already declared ( 104, and 129.J what were the Effects upon Metals and Semi-Metals of acid Menftrua, condenfed in a fluid Form, by a Heat not greater than that of the Fire which makes them;ebulliate. It now remains, that we mould examine what arc the Eftects of the felf-fame Menftrua, urged with the Dc-gree of Fire which makes them red hot, upon the Bodies aforefaid. 153. But, as the acid Saits condenfed into Liquors (105, 108, 113, 126, 128.) cannot bear to be made red hot, and are refolved by a much lefs Fire, into Vapours which cannot be reftrained; this requires another manual Operation: For the Acid of Vinegar cannot be extracted out of the Cryftals of Verdigreafe, nor the Spirits of Nitre and Salts be extracted out of them, by terreftrial Additions, or by Vitriol (113, 126); nor in fhort the Acid of Vitriol itfelf be fetched out of its metallick or terreftrial Matrix, without the Action of a very ftrong Fire. Therefore, you are to proceed in fuch a Manner, that the Bodies to be changed by thefe acid Spirits, be in the fame Veflcl wherein the faid Spirits are produced, and, when made red hot therein, be furround- ed on every Side with the agitated Vapours of the fame Spirits. This is eafily obtained, if you put the faid Bodies among the Matter itfelf which is to emit the acid Spirits, after having moiftened it lightly, and prefled it; and then expofe them together to the Fire. This Operation is then called Cementation; and the dry Species, which melt the acid Menftnta, and are commonly ufed for this Operation, are called Cements. 154. The Proportion of the Additions ufed in making the Cements, is the fame as in the Diftillation of acid Spirits ( 113, and 126). But common Salt and Nitre being the melting Metiftrua of Metals ( 1...