LAWSON — ON THE IMPROVEMENTS IN AMALGAMATION. 73 



be combined directly with the mercury employed, the proportions 

 varying according to the requirements of the case. 



" This invention can be used in conjunction with any machine or 

 apparatus for performing the amalgamating process, and in cases 

 where amalgamating vessels or receptacles constructed of iron are 

 employed, an additional advantage arises from the fact that mercury 

 combined as before mentioned with sodium forms a thin film over 

 the surface of the iron, thus collecting very minute quantities of the 

 metal under treatment, and which may be removed by the ordinary 

 process, and subjected to the subsequent treatment usually employed. 



" The mode of treatment 'employed is as follows : — An amalgam 

 of sodium is in the first place formed by combining sodium with 

 mercury. The proportions may be varied within wide limits, that is 

 to say, from less than three to more than thirty parts of sodium to 

 one hundred parts by weight of mercury. The sodium and mer- 

 cury must be caused to unite, and the amalgam prepared with the 

 customary precautions well known to and understood by chemists. 

 The last mentioned method of forming the sodium amalgam is that 

 which the inventor usually prefers in actual practice ; but, if desired, 

 the amalgam may be prepared electro-chemically, as described by 

 Becquerel and other chemical authors, or by any other suitable means. 

 The amalgam is then added to the mercury employed for the 

 purposes of amalgamation, the proportions varying according to the 

 quantities of precious metal contained, and the state in which it oc- 

 curs in the ore or matrix ; but as in the process the beneficial ejSects 

 of the sodium are gradually removed, the action should be 

 maintained, if needed, by occasionally introducing fresh supplies of 

 the amalgam into the charge of mercury contained in the machine 

 employed. The quantity must, however, be regulated and deter- 

 mined by the skill and judgment of the operator, as no definite and 

 absolute proportion can be laid down as necessary. If, however, 

 the proportion of the alkali metal exceeds that of one part to from 

 120 to 150 parts of mercury, the amalgam becomes viscid, and its 

 manipulation may be inconvenient. The effect of thus combining 

 the sodium with the mercury is to impart to the latter a greater 

 affinity for or power of adhesion to the precious metal under treat- 

 ment than it possesses in its simple and uncombined condition, so 

 that it will readily amalgamate with the gold or silver, even when 



