ON THE REDUCTION OF LIMAILLE. 17 



you will by this means liberate much impurity of 

 a dark colour. Undiluted hydrochloric acid is now 

 to be added to the drained filings, and the vessel 

 again placed on the sand-bath for a quarter of an 

 hour's boiling ; the filings will have become bril- 

 liant, and at this stage all trace of acid and dirt 

 must be tliorouglily washed away with boiling water. 



If it were now submitted to the flux and crucible 

 the button would exhibit a poverty of quality, on 

 account of silver filings, which generally are found 

 in limaille ; to avoid this it is necessary to employ 

 a small quantity of dilute nitric acid (one part acid, 

 three water), and submit the whole to a gentle heat 

 at first, which afterwards may be increased to the 

 boiling point ; full a quarter of an hour will be 

 desirable for this part of the process ; pour off the 

 solution of nitrate of silver, and employ undiluted 

 nitric acid ; place the vessel again on the sand-bath 

 and boil for a quarter of an hour (or until nearly 

 dry) ; thoroughly wash away with boiling water all 

 trace of acid, and dry the filings, which will now 

 be ready for the crucible. 



The flux and filings are now to be thoroughly 

 mixed, the composition and proportions as fol- 

 low : — Say, if sixteen ounces of gold-filings, mix 

 eight ounces of bisulphate of potass (sal enixum),* 

 four ounces of chloride of sodium (common salt), 

 and two ounces of bichloride of mercury (corrosive 

 sublimate). These ingredients must be in powder, 

 * Commonest kind of sal-enixum. 

 C 



