TABLE I. Showing the quantity of fine gold in 1 oz. of any alloy to of a carat grain, and the mint TABLES A, B, and C. To convert mint value into bank value, when the standard is expressed in carats, grains, and eights TABLE II. Table of relative proportions of fine gold and alloy, with the respective mint values of 1 oz. TABLE. To convert mint value into bank value when the standard is expressed in thousandths TABLE III. Assay table, showing the amount of gold and silver, in ounces, pennyweights, and grains, contained in a tone of ore, &c., from the XX MANUAL OF PRACTICAL ASSAYING. CHAPTER I. CHEMICAL NOMENCLATURE: LAWS OF COMBINATION: ETC. It is not necessary, neither is it possible, in a treatise like the present, to give more than a very brief outline of the elements of chemical nomenclature, and the more simple laws of chemical combination. Undoubtedly a knowledge of chemistry is of the greatest value to the practical assayer -indeed, we may say no one can attain to any degree of eminence in this branch of industry unless he has had some amount of practice in the laboratory. But it will be quite beyond our province here to teach the elements of chemistry. So much of the nomenclature and leading laws will be given as are indispensable to a proper understanding of what is to follow, but beyond this the student must seek for further instruction in chemistry from books which are specially devoted to that science; and he should above all things endeavour to acquire a practical acquaintance with the laws and manipulations of experimental chemistry, by taking a series of lessons in a laboratory. CHEMICAL NOMENCLATURE.-Every material substance with which we are acquainted consists of one or more bodies, termed simple or elementary-such bodies being so called from the fact that with our present means of research we are unable to reduce them to a more simple form. Thus, if a piece of common iron pyrites, or mundic, as it is B commonly called, be submitted to certain operations, it will be found that we can obtain from it two substances totally distinct, in both physical and chemical properties, from each other and from the substance from which they were obtained. One body is sulphur, an opaque yellow substance, fusing at a very low temperature, igniting readily, and exhaling when burning a peculiar and suffocating odour. The other constituent of the pyrites is iron, a well-known metallic substance, requiring an intense heat for fusion, and becoming red-hot without burning. If we were now to perform any experiment which, in the present state of knowledge, ingenuity could suggest, we should be totally unable to cause either the sulphur or the iron to assume a more simple or elementary state of existence. We can with ease cause either of them to enter into new combinations with other bodies, and these compounds we can decompose as in the case of the pyrites-and obtain both sulphur and iron again in their separate forms with all their characteristic properties; but nothing more than this can be effected hence we are led to the belief that both sulphur and iron are simple bodies, or bodies containing only one kind of matter. The following is a list of the simple substances discovered up to the present time; it is accompanied by certain symbols and numbers, the use and nature of which will be hereafter pointed out. Those substances in italics have hitherto found no practical use; and those marked with an asterisk (*) are often found native, or unassociated with mineralising elements. name of the The first column contains the common element; the second, the symbol, or chemical short-hand character, in which all chemical changes and decompositions are most readily written and understood; and the third, the atomic weights. These atomic weights are not absolutely correct: they are not given beyond the first place of decimals, to avoid tedious calculation. For all practical purposes they may be considered accurate. Of the compounds of these elements, only those will be discussed which are likely to fall under the notice of the assayer. The principal compound bodies are acids, oxides, salts, and binary substances containing no oxygen. When a body combines in more than one proportion with oxygen, that compound containing the least oxygen takes the termination ous, that the most ic; thus, sulphurous acid, sulphuric acid; arsenious acid, arsenic acid; ferrous oxide, ferric oxide; mercurous oxide; in only one proportion (or when they form only one basic oxide) they are distinguished by the termination ic, as potassic oxide, aluminic oxide. OXIDES are binary oxygen compounds: they may be divided into two series. The first comprises those oxides which do not possess the property of combining with acids to form salts--they are termed indifferent oxides; the second series contains those capable of uniting with acids to form salts, and are called salifiable oxides or bases. When a simple body, in combining with oxygen, forms but one oxide, it is simply called an oxide, added to the name of the simple body; thus, oxide of zine or zincic oxide. If the body is capable of combining with oxygen in many proportions, the words proto, sesqui, bin or per, &c., precede the term oxide to express the progressive amounts of oxygen. Most metals form one salifiable oxide, and many of them have two. These are now generally distinguished by the terminations ous and ic, in the same manner as are the acids; thus, we have protoxide of lead, iron, copper, tin, &c.; sesquioxide of aluminium, iron or chromium, &c.; binoxide, or peroxide of manganese, copper, mercury, &c.; and when we speak of them as salifiable bases, ferrous oxide and ferric oxide; mercurous and mercuric oxide; potassic oxide; aluminic oxide. There are still higher degrees of oxidation of some metals; these are nearly always acids-as chromic, stannic, and antimonic acids. SALTS are formed when an acid unites with a base, and usually the properties of the acid and the base are reciprocally neutralised; thus, an acid which before combination possessed the power of reddening blue litmus, loses it . in proportion as it combines with the base; and in like manner a base which would at first change reddened litmus paper to blue, loses this property as the acid saturates it. In this case the acid and base have combined to form a salt. In naming salts, we have to consider firstly, the nature of the acid; secondly, the salifiable nature of the base; and thirdly, the proportions in which the acid and base are combined. Acids terminating in ie form salts terminating in ate. |