Manual of Practical Assaying: Intended for the Use of Metallurgists, Captains of Mines, and Assayers in GeneralH. Bailliere, 1846 - 426 páginas |
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Página 8
... residue richer ; and in the other the whole might be pulverized , and the produce would be of course less , and nearer the actual amount contained in the sample submitted to assay . A knowledge of this fact is also very useful , but in ...
... residue richer ; and in the other the whole might be pulverized , and the produce would be of course less , and nearer the actual amount contained in the sample submitted to assay . A knowledge of this fact is also very useful , but in ...
Página 14
... residue is mixed with charcoal ; the residue by the latter process is comparatively pure , but it is not generally preferred , on account of the time and high temperature necessary . Fusion . This operation is sufficiently simple , and ...
... residue is mixed with charcoal ; the residue by the latter process is comparatively pure , but it is not generally preferred , on account of the time and high temperature necessary . Fusion . This operation is sufficiently simple , and ...
Página 62
... residue of the coal employed in the gas works after all the volatile matter is expelled . It is generally iron black , and has nearly a metallic lustre it is difficult to inflame , and burns but in small pieces , but gives a very ...
... residue of the coal employed in the gas works after all the volatile matter is expelled . It is generally iron black , and has nearly a metallic lustre it is difficult to inflame , and burns but in small pieces , but gives a very ...
Página 65
... residue produced by the action of heat , so that their use is very limited and uncertain . Whenever they are employed as reducing agents , without covering the substance , a loss can be experienced , on account of the bubbling and ...
... residue produced by the action of heat , so that their use is very limited and uncertain . Whenever they are employed as reducing agents , without covering the substance , a loss can be experienced , on account of the bubbling and ...
Página 66
... residue when burnt ; it is , therefore , preferable to wood charcoal , in cases where no foreign matter can be introduced into the assay . Starch . - Common starch well dried , and better still torrefied is employed with advantage as a ...
... residue when burnt ; it is , therefore , preferable to wood charcoal , in cases where no foreign matter can be introduced into the assay . Starch . - Common starch well dried , and better still torrefied is employed with advantage as a ...
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Términos y frases comunes
added alkaline alloy ammonia antimony aqua regia arsenic ascertained assay baryta bead becomes bismuth black flux blow-pipe blue boiling borax button carbonate of soda carbonic acid caustic cent charcoal chloride cobalt colour combustible contain cooling copper crucible cupel decomposed dissolved employed excess filter fuel furnace fused fusible fusion galena gangue gives glass globules gold grains grey heat hydrochloric acid ignited inches iridium lime liquid litharge manganese mass matter mattrass mercury metallic method microcosmic salt mineral mixed mixture moistened nitrate nitre nitric acid obtained odour opaque operation oxide of iron oxide of lead oxide of zinc oxygen peroxide placed platinum portion potash powder precipitate produced proportion protoxide pulverized pure pyrites readily reducing flame residue rhodium roasting scorification separated silica silver slag small quantity soluble solution substance sulphate sulphuret of antimony sulphuric acid tellurium temperature tube vapour volatile washed weight yellow zinc
Pasajes populares
Página 184 - Fahr., and then note its weight; it will be found to have lost a certain amount, which will correspond to the weight of the bulk of water it has displaced. Divide its weight in air by the loss of weight in water, and the quotient will be the required specific gravity. This will be more readily understood by an example. Suppose we find the mineral to weigh 80 grains in the air, and only 66 in water ; the loss ==80 — 66 = 14.
Página 296 - ... of water, and a gentle heat applied. The sulphate of iron is gradually added in small quantities to the acid, so as to absorb the chlorine as it is evolved, and the addition of that salt continued till the liquid, after being heated, gives a blue precipitate with the red prussiate of potash, and has no smell of chlorine, which are indications that the protosulphate of iron is present in excess. By weighing what remains of the sulphate of iron, the quantity added is ascertained ; say m grains....
Página 94 - ... combination of some metals with others, as in the case of a mixture of the oxides of manganese and iron with a suitable flux, the iron is obtained in a state of purity, whereas if no flux had been added, an alloy would have been obtained. Gold and silver can be separated from many other metals by means of a flux. 5. To scorify some of the metals contained in the substance to be assayed, and obtain the others alloyed with a metal contained in the flux, as gold or silver with lead. 6. And lastly,...
Página 42 - Being thus luted, the vessels are afterwards to be placed in a warm situation, over the sand-bath or near the ash-pit, or in the sun's rays. They should not be allowed to dry rapidly or irregularly, and should be moved now and then to change their positions. To prevent cracking during desiccation, and the consequent separation of the coat from the vessel, some chemists recommend the introduction of fibrous substances into the lute, so as mechanically to increase the tenacity of its parts. Horse-dung,...
Página 324 - ... added to that mixed before. The whole is very gently heated in a porcelain crucible, until the mass is black throughout. By acting thus the double salts are decomposed, and the platinum, whose oxygen passes away with the carbonic acid, is reduced. The rhodium and iridium meanwhile become oxidised, and remain in such a state as to permit of their separation from the platinum by solution. When, instead of following the process just recommended, the precipitation of the double salts is effected...
Página 19 - ... the weight, and directly proportionate to the pressure ; so that if we had 100 cubic inches of air when the barometer was 29 inches it would be as : — 30 : 29 :: 100 : 96-6 or if the barometer stood at 31 inches when the 100 cubic inches were measured, it would be as : — 30 : 31 :: 100 : 103-33 so that the rule is : — as the mean pressure is to the observed pressure, so is the observed volume to the true volume. The correction for temperature or pressure may be made indiscriminately, the...
Página 380 - When this metal is absent, it is requisite to add a quantity of it, which ought to be equivalent to double the weight of the gold and platinum united, and cupel at the strongest heat which can be obtained in a good muffle with a suitable proportion of lead. This proportion varies much, according to the composition of the alloy, and the temperature at which the operation is carried on. Experience has shown that the copper can be more completely separated, and less silver lost, by cupelling at a high...
Página 56 - It consists of two parts, which may be distinguished as the register and the scale. The register is a solid bar of blacklead earthenware, highly baked. In this a hole is drilled, into which a bar of any metal, six inches long, may be dropped, and which will then rest upon its solid end. A cylindrical piece of porcelain, called the index, is then placed upon the top of the bar...
Página 4 - Six Ethnographical Maps, as a Supplement to the Natural History of Man, and to the Researches into the Physical History of Mankind, folio, coloured, and 1 sheet of letter-press, in cl.
Página 355 - ... matters, it is indispensable to reduce this loss as much as possible by reducing the proportion of lead to that which is strictly necessary. Long experience has proved that silver opposes the oxidation of copper by its affinity, so that it is necessary to add a larger amount of lead in proportion to the quantity of silver present.