#Perfectit 3 has fired an exception crack#

Part of the borax is often kept separate and used as a cover, being put on the top of the rest of the charge after transference to the crucible. The various ingredients are thoroughly mixed together on rubber cloth or in the crucible in which the fusion is to take place. The charcoal is always weighed with great care the litharge is best measured by a ladle or shot measurer the fluxes may also be measured out by a ladle more rapidly than they can be weighed. The ore is weighed accurately to 0.01 gramme unless very poor when a less exact approximation is sufficient. This Gold Fire Assay Process is divided into four parts: Method of Gold Fire Assay by Fusion or Crucible For the same reason the part of the mixed sample which is taken for assay should not be hastily shovelled on to the balance pan from the top of the pile, but a vertical slice should be taken, some of the lowest layer being carefully scraped up from the rubber cloth. The sample should never be mixed by shaking, and care should be taken to avoid jarring it after mixing, as metallics in that case tend to settle to the bottom from their superior density, and a fair sample cannot easily be obtained.

#Perfectit 3 has fired an exception crack#

Before weighing out the powdered ore for assay, the whole sample should be turned out into a wide bowl or on to glazed paper, or, better still, rubber cloth (which does not crack and wear out like paper), and thoroughly mixed with a spatula. The prepared sample may be mixed and divided by the Bridgman divider, and is stored in tin boxes or glass jars, which should be labelled by numbers, none of which are ever repeated. The total value of the ore is found by adding these two results together. The safer plan is to cupel by themselves the whole of the metallics left on the sieve and calculate their value per ton of ore independently of the result obtained by the ordinary assay. The smaller pieces which pass through the sieve in the first instance constitute an unavoidable evil that is increased by every piece of metal that follows them. This is a dangerous practice, as it is impossible to ensure the even distribution of metallics through the sample. Sampling the Ore and Preparation of the Sample for Fire Assay In some assay offices, part of the pulverized ore is thrown back into the mortar with the metallics, and grinding is continued until everything passes the sieve. These “metallics” are not readily reducible to a fine state of division, and, though a part always passes through the sieve, some of the larger pieces which have resisted abrasion fail to do so. In many ores, both gold and auriferous silver occur natively in grains or threads. He also mentions the forerunner of the buck-board, and instances assay-offices in which 200 assays of ores were made in a week. Ercker describes many of the methods and precautions are given in this chapter, such, for instance, as the treatment of cupriferous ores with nitric acid, the use of a salt cover in the crucible, and of “ proof-Centners,” which correspond to assay-tons. When fusion in a crucible was recommended, it was only as a preliminary to scorification. The assay by scorification was preferred to pot-fusion by the German assayers of long ago. Very rich ores may be assayed by scorification, the errors arising from the small amount of material used in the process being less important in their case. As a general rule, gold ores are better assayed by the fusion process, so that a comparatively large quantity of material may be operated on. The exact method to be used in any particular case varies with the composition of the ore. In these operations, silver and the metals of the platinum group remain with the gold, and are subsequently separated by inquartation and parting, and, in the case of platinum and its allies, by further special methods. The button of lead obtained by either method is then subjected to cupellation, by which the lead is oxidized and removed, and the resulting bead of precious metal is weighed. The plan of operation is to concentrate the precious metal in a button of lead either (1) Fire Assay By fusion in a crucible or, more rarely, (2) Fire Assay By scorification. The Gold Fire Assay Process of ores is almost universally conducted in the dry procedure by furnace methods. Wet Assay Methods of Gold Alloys & Compounds.Fire Assaying Rhodium and Iridium-Gold Alloys.Method of Gold Fire Assay by Fusion or Crucible.