1857.] of Gold (and other Metals) to Light. 413 



of a funnel, the reduced gold passing freely. All the vessels 

 used in these operations must be very clean ; though of glass, 

 they should not be supposed in proper condition after wiping, 

 but should be soaked in water, and after that rinsed with 

 distilled water. A glass supposed to be clean, and even a new 

 bottle, is quite able to change the character of a given gold 

 fluid. 



Fluids thus prepared may differ much in appearance. Those 

 from the basins, or from the stronger solutions of gold, are 

 often evidently turbid, looking brown or violet in different 

 lights. Those prepared with weaker solutions and in bottles, 

 are frequently more amethystine or ruby in colour and ap- 

 parently clear. The latter, when in their finest state, often 

 remain unchanged for many months, and have all the appear- 

 ance of solutions. But they never are such, containing in fact 

 no dissolved, but only diffused gold. The particles are easily 

 rendered evident, by gathering the rays of the sun (or a lamp) 

 into a cone by a lens, and sending the part of the cone near 

 the focus into the fluid ; the cone becomes visible, and though 

 the illuminated particles cannot be distinguished because of 

 their minuteness, yet the light they reflect is golden in cha- 

 racter, and seen to be abundant in proportion to the quantity 

 of solid gold present. Portions of fluid so dilute as to sho,w 

 no trace of gold, by colour or appearance, can have the pre- 

 sence of the diffused solid particles rendered evident by the 

 sun in this way. When the preparation is deep in tint, then 

 common observation by reflected light shows the suspended 

 panticles, for they produce a turbidness and degree of opacity 

 which is sufficiently evident. Such a preparation contained in 

 a pint bottle will seem of a dull pale-brown colour, and nearly 

 opake by reflexion, and yet by transmission appear to be a fine 

 ruby, either clear or only slightly opalescent. 



That the ruby and amethystine fluids hold the particles in 

 suspension only, is also shown by the deposit which occurs 

 when they are left at rest. If the gold be comparatively abun- 

 dant, a part will soon settle, i. e. in twenty-four or forty-eight 

 hours ; but if the preparation be left for six or eight months, 

 a part will still remain suspended. Even in these portions, 

 however, the diffused state of the gold is evident ; for where, 

 as in some cases, the top to the depth of half an inch or more 



