C21 



ASSAYING. 



ASSENT, EOYAL. 



C23 



latter does not appear to be fine (or free from alloy), repeat the 

 operation until it is. An unerring mark of fineness is a sinking or 

 concavity in the centre of the upper surface of the ' assay," or button ; 

 but so long as the upper surface is convex, it is not fine. If the 

 button, when fine, instead of having a smooth brilliant surface, of a 

 yellowish-red colour, exhibits a roughish surface, of a dark-red colour, 

 and having firmly attached to it bits of a dark-red slag, the refining 

 process has been pushed too far. The button being fine, take the slag 

 which was reserved from melting the calcined regulus, together with 

 the flux and slag from the refining process, and mix these with three 

 drachms of red argol and a very little charcoal powder, and melt well 

 in the crucible in which the refining is performed. This will give a 

 small metallic button, which refine as before. 



The flux above alluded to, which is used for refining, is prepared by 

 burning together a mixture of three parts nitre, two parts red argol, 

 and one part of common salt. This is best done by putting the 

 ingredients into a large iron mortar, and stirring them with a red- 

 hot poker until combustion ceases. The mass should be reduced 

 to powder before it is quite cold, and preserved in a well-stopped 

 bottle, or it will deliquesce. About half a drachm of this flux and of 

 common salt are usually taken, and this will generally be a sufficient 

 quantity; but as much should be used as will perfectly cover the button 

 when it is poured into the mould, otherwise the metal will oxidise, 

 which of course is to be avoided. 



The ores of the second subdivision of sulphurets are best assayed by 

 calcining them perfectly in the first instance, so that the first melting 

 shall give a metallic button, instead of a regulus or sulphuret. To 

 effect this, when the one has been calcined until the whole of the 

 sulphur is driven off, it should be melted with a drachm each of 

 slaked lime and fluor spar, the same quantity of borax and red argol, 

 with a little nitre ; and then proceeded with precisely as directed for 

 calcined regulus. 



Copper ores not containing sulphur, or only in very small quantity, 

 may be calcined for a short time (a few minutes is sufficient), and 

 melted as directed in the last section, except that the quantity of lime 

 and fluor spar may be reduced, and some scales of iron from a smith's 

 forge added. 



Lead. The principal ore of lead is the sulphuret, commonly called 

 galena ; but the carbonate, or white lead ore, is sometimes found in 

 considerable quantity. 



To .assay the former ore : take 400 grains coarsely powdered, mix 

 it with 100 grains of black flux, and 50 grains of cream of tartar ; put 

 the mixture into a Cornish or Hessian crucible that will hold double 

 the quantity, plunge to the bottom of it the ends of six or eight pieces 

 Hi No. 10 iruii wire, and cover it with carbonate of soda to the depth 

 of half an inch. Expose it to a bright-red heat for about ten minutes, 

 or until the matter in the crucible has ceased to boil, and is become 

 smooth ; then withdraw the pieces of iron wire, and allow the contents 

 of the crucible to cool. On breaking the crucible, the button of lead 

 will be found at the bottom. 



If the ore is much mixed with iron pyrites or earthy matter, a little 

 fluor spar and borax should be added to the other ingredients. 



The carbonate is best assayed by melting it with half its weight of 

 black flux and a little cream of tartar, covering the mixture as before 

 with carbonate of soda. 



Tin. The ores of tin are principally of two kinds, the oxide and the 

 aulphuret ; the Litter is, however, very rare. 



To assay the oxide of tin, or black tin, as it is commonly called, it 

 requires only simple fusion with half its weight of black flux, one- 

 eighth borax and the like of cream of tartar, covering the mixture in 

 the crucible to the depth of half an inch with carbonate of soda. 



The sulphuret, or pyritous tin ore. Let 400 grains be reduced to 

 powder and carefully calcined, with occasional additions of small 

 portions of charcoal powder, constantly stirring it with an iron rod, 

 and so managing the fire as to prevent the ore from clotting. This 

 operation should be continued until the ore ceases to emit either sul- 

 phureous or arsenical vapours. When thoroughly calcined, file off 

 from the stirring-rod any portion of the ore that may adhere to it, 

 mMing it, of course, to that in the crucible. Add likewise 40 grains of 

 lime, 20 grains of fluor spar, 150 grains of black flux, with a small 

 quantity of nitre, borax, and cream of tartar; when these are well 

 mixed, cover with carbonate of soda, and when melted quite smooth, 

 allow the crucible to cool, when the tin will be found at the bottom. 



Zinc. The ores of zinc are of two kinds, the carbonate, or calamine, 

 and the sulphuret, or blende. 



There is perhaps no mode of directly assaying the ores of this 

 metal, so aa to obtain their metallic contents. That generally given 

 in books of chemistry and metallurgy, namely, distillation of the 

 roasted ore mixed with charcoal in an earthen retort, will be found 

 universally to fail, either entirely or partially. Even in the treatment 

 of these ores in the large way, the quantity of metal obtained seldom 

 exceeds one-half the quantity which they contain : the loss arises 

 partly from the escape of uncondensed metallic vapour, and partly 

 from unreduced oxide. 



The best mode of making comparative assays of the ores of zinc is as 

 follows : If the ore is the carbonate, or calamine as it is usually termed, 

 reduce it to pieces of the size of hazel-nuts, weigh thirty-two ounces, 

 avoirdupois, and expose it under a muffle, or in a large crucible, to a 



moderate red heat, until the pieces are red-hot throughout. When cold 

 reduce the ore, which will have become very friable, to a fine powder ; 

 reweigh it and note its weight, mix it with its own bulk and one-half 

 more of powdered charcoal, and press it down moderately tight into a 

 Stourbridge-clay crucible, which it should not fill nexrer than two 

 inches to the top. Then take a piece of moistened and tempered clay, 

 in which a little charcoal powder and sand have been mixed, roll it out 

 to one-eighth of an inch thick, and cut out of it a round cake to fit 

 into the crucible upon the mixture of calamine and charcoal, giving it 

 a little concavity on its upper surface. Then weigh as much granulated 

 copper as is equal to two-thirds of the calcined calamine, spread it 

 upon the disc of clay in the crucible, cover it with charcoal powder, 

 and lute a clay cover to the crucible. Set the crucible in an air 

 furnace, and expose it to a bright-red heat for three hours, and then 

 increase the heat to a yellowish- white for another hour ; then take out 

 the crucible and allow it to cool, collect the brass which will have 

 formed on the clay disc and weigh it ; if its weight equals that of the 

 calcined calamine, the latter may be considered of good quality for 

 commercial purposes. The arrangement may be varied by mixing the 

 granulated copper with the calamine and charcoal, instead of putting 

 it on the clay disc ; but when the operation is finished, it will be more 

 trouble to collect the grains of brass. 



This is an operation that requires considerable nicety in the manage- 

 ment; of the fire ; for if too hot, the metallic zinc is vaporised faster 

 than the copper can combine with it ; and, on the other hand, if not 

 hot enough, the oxide will not be reduced. Attention to a few trials 

 will give the requisite judgment. 



The sulphuret, or blende, is assayed in the same way, except as to 

 calcination. 



Blende must first be reduced to a fine powder and carefully calcined 

 upon the floor of a muffle go heated as to exclude any carbonaceous 

 smoke or flame, stirring it constantly with an iron rod until it ceases to 

 give any indication of sulphur. The powdered blende should not lie 

 above one-fourth of an inch thick on the muffle, and the heat should be 

 very gradually raised from a dull to a bright-cherry red. When 

 perfectly calcined, it must be treated in the same way as calcined 

 calamine. 



Zinc ores can only, however, be accurately assayed by the humid 

 process. Mitchell recommends the following methods of conducting 

 this operation : The calcined ore " is dissolved in excess of hydrochloric 

 acid, evaporated to dryness, and redissolved by water. Some silica re- 

 mains which has not been dissolved, and which may be collected on a filter. 

 An excess of ammonia is now poured into the solution, and the pre- 

 cipitate separated by filtration from the solution, which latter contains 

 all the oxide of zinc. The solution may now be boiled with an excess 

 of carbonate of soda, until all the ammonia has been expelled, the pre- 

 cipitated carbonate of zinc collected on a filter, washed, dried, ignited, 

 ami weighed ; four-fifths of its weight corresponds to metallic zinc. 



"The analysis of blende may be conducted by treating it with 

 gently warmed strong nitric acid ; decant the solution with care, and 

 boil with aqua regia ; collect the residue on a filter, and wash. The 

 solution may be treated exactly as in the analysis of calaminiferous 

 ore : with ammonia, and carbonate of soda. 



"Brass may be analysed by solution in nitro-hydroehloric acid, 

 evaporation to dryness, treating with hydrochloric acid, diluting with 

 water, and precipitating its contained copper by means of a rod of 

 iron, collecting, washing, drying, and weighing the precipitated metal : 

 the loss is zinc. 



" This is only applicable, however, where the brass contains only 

 copper and zinc ; it sometimes, however, contains lead." 

 ASSEMBLY, GENERAL, SCOTLAND. [GENEBAL ASSEMBLY.] 

 ASSEMBLY, NATIONAL. [NATIONAL ASSEMBLY.] 

 ASSEMBLY OF DIVINES. [WESTMINSTER ASSEMBLY.] 

 ASSENT, ROYAL. When a bill has passed through all its 

 stages in both houses of parliament, if it is a bill of supply, it is 

 sent back to the charge of the officers of the House of Commons, 

 in which it had of course originated; but if not a bill of supply, 

 it remains in the House of Lords. The royal assent is always 

 given in the House of Lords> the Commons, however, being also 

 present at the bar, to which they are summoned by the Black Rod. 

 The sovereign may either be present in person, or may signify the 

 royal assent by letters patent communicated to the two houses by 

 commissioners. Power to do this is given by 33 Henry VIII. c. 21. 

 The commissioners are usually three or four of the great officers of 

 state, and sit in their robes on a bench placed between the woolsack 

 and the tlirone. The sovereign, when the royal assent is given in 

 person, is seated on the throne robed and crowned. The bills that 

 have been left in the House of Lords lie on the table ; the bills of 

 supply are brought up from the Commons by the Speaker, who, in 

 presenting them, especially at the end of a session, usually accompanies 

 the act with a short speech. In these addresses it is usual to recom- 

 mend that the money which has been so liberally supplied by the 

 faithful Commons should be judiciously and economically expended ; 

 and a considerable sensation has been sometimes made by the emphasis 

 and solemnity with which this advice has been enforced upon the 

 royal ear. The royal assent to each bill is announced by the clerk of 

 parliament. Having read the title, he says, if it is a bill of supply, 

 " Le roi (or la reine) remercie ses loyal subjects, accepte leur bene- 



