726 GOLD ASSAYING 



are boiled with acid in one flask. The plan which is now being generally adopted, 

 consists in placing the fillet coils in a series of platinum cups or thimbles, each cup 

 being provided with several fine slits. These cups are then arranged in rows in a, 

 perforated platinum tray, and the whole placed in ;i vessel of platinum or other mater- 

 ial containing nitric acid. After boiling in acid for a given time, the tray is lifted out, 

 dipped in water, and then transferred to a vessel containing a stronger acid ; after boil- 

 ing, the tray containing the gold cornets is then removed, washed in water, dried, and 

 carefully heated in a muffle. The cornets are then removed and weighed. 



The platinum cups are made of various sizes, according to the quantity of alloy 

 operated on, and the platinum trays constructed to receive from 16 or more of the 

 cups as may be desired. A tray to hold 49 cups is about 4 inches square, and each cup 

 |ths of an inch in depth and inch in diameter at the top. The use of platinum cups 

 is a modification of the plan first introduced by Mr. T. H. Henry and Mr. C. Tookey 

 in 1854. They constructed glass tubes, provided at the lower part with perforated 

 discs of platinum, and having a rim near the upper end. In the assay process a fillet 

 coil was placed in each tube. A number of these tubes were supported by a porcelain 

 plato having circular holes, the holes and tubes being numbered. Thus arranged, a 

 number of them could be boiled at one time in a vessel containing nitric acid, and 

 readily removed for subsequent treatment. The platinum cups and parting apparatus 

 were first manufactured and introduced by Messrs. Johnson and Matthey. 



At the Mint Conference held at Vienna in 1857 the following process was agreed 

 upon : Add to 1 part of gold supposed to be present 2 parts of silver, wrap up in 

 paper, and introduce into a cupel in which the requisite amount of lead is just fusing. 

 After cupellation, the button of gold and silver is flattened out by hammering or roll- 

 ing, then ignited, and rolled into a coil. The coils are then treated, first, with nitric acid 

 of I f 2 sp. gravity, afterwards with nitric acid of 1'3 sp. gravity, and lastly it is washed 

 with water, ignited and weighed. 



The process recommended in the old French official report is as follows : Twelve 

 grains of the gold intended to be assayed must be mixed with thirty grains of fine 

 silver, and cupelled with 108 grains of lead. The cupellation must be carefully 

 attended to, and all the imperfect buttons rejected. When the cupellation is ended, 

 the button must be reduced, by lamination, into a plate of H inch, or rather more, 

 in length, and four or five lines in breadth. This must be rolled up upon a quill, and 

 placed in a matrass capable of holding about three ounces of liquid, when filled up to 

 its narrow part. Two ounces and a half of very pure aquafortis, of the strength of 20 

 degrees of Baume's aerometer, must then be poured upon it ; and the matrass being 

 placed upon hot ashes, or sand, the acid must be kept gently boiling for a quarter of 

 an hour: the acid must then be cautiously decanted, and an additional quantity of 1 

 ounce must be poured upon the metal, and slightly boiled for twelve minutes. This 

 being likewise carefully decanted, the small spiral pieces of metal must bo washed with 

 filtered river-water, or distilled water, by filling the matrass with this fluid. Tho 

 vessel is then to be reversed, by applying the extremity of its neck against the bottom 

 of a crucible of fine earth, the internal surface of which is very smooth. Tho an- 

 nealing must now be made, after having separated the portion of water which had 

 fallen into the crucible; and lastly, the annealed gold must bo weighed. For ihe 

 certainty of this operation, two assays must be made in the same manner, together 

 with a third assay upon gold of twenty-four carats, or upon gold the fineness of which 

 is perfectly and generally known. 



No conclusion must be drawn from this assay, unless the latter gold should prove to 

 bo of the fineness of twenty-four carats exactly, or of its known degree of fineness ; 

 for, if there be either loss or surplus, it may bo inferred that tho other two as>.iys, 

 having undergone the same operation, must be subject to tho same error. The opera- 

 tion being made according to this process by several assayers, all tin- assayers must 

 have obtained an uniform result without communication with each other. 



M. Vauquelin recommends to boil 60 parts of nitric acid at 22 Baume\ on the spiral 

 slip, or cornet of gold and silver alloy, for twenty-five minutes, and replace the liquid 

 afterwards by acid of 32, which must bo boiled on it for eight minutes. Thi> , 

 is free from uncertainty, when the assay is performed upon an alloy containing 

 siderablo quantity of copper. But this is not tho case, in assaying fimT{i<>ltl ; I'm* ll.cn 

 a little silver always remains in tho gold. The surcharge which occurs hero is 

 thousandths. M. Claudet recommends the following process : Ho takes 0'500 of tho 

 fine gold to bo assayed ; cupels it with 1'SOO of silver and 1-000 of lead ; f< .nns, wit !i 

 the button from the cupel, a riband or strip thrco inches long, which ho rollp into a 

 cornet. He puts this into a matrass with acid at 22 ]'., which ho boils for 3 or 4 

 minutes. He replaces this by acid of 32 B., and boils for ten minutes; then de- 

 cants off, and boils again with acid of 32, which must be finally boiled for H or 10 

 minutes. He washes the cornet, and puts it entire into a small crucible permeable 



