160 
DE. FAEADAY ON THE EXPEEBIENTAL EELATIONS 
beautiful ruby or amethystine fluid is immediately produced, -which will increase in depth 
of tint by a little time. Generally, however, the preparations made -with phosphorus 
dissolved in sulphide of carbon, are more ruby than those where ether is the phosphorous 
solvent. The process of reduction appears to consist in a transfer of the chlorine from 
the gold to the phosphorus, and the formation of phosphoric or phosphorous acids and 
hydrochloric acid, by the further action of the water. 
The fluids produced may easily be tested for any gold yet remaining unreduced, by trial 
of a portion with solution of protochloride of tin. If any be found, it is easily reduced 
by the addition of a little more of the phosphorus in solution. After all the gold is 
separated as solid particles, the fluid may be considered in its perfected state. 
Occasionally it may smell of phosphorus in excess, even after it has been poured off from 
the deposited particles of it and the sulphide. In that case it is easy to deprive it of 
this excess by agitation in a bottle with air. When kept in closed vessels mouldiness 
often occurs. If this be in groups it is collected -with facihty at the end of a splinter 
of wood and removed, or the whole fluid may be poured through a wet plug of cotton 
in the neck 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 e-vddently turbid, looking bro-^ or -violet in 
different lights. Those prepared -with weaker solutions and in bottles, are frequently 
more amethystine or ruby in colour and apparently clear. The latter, when in their 
finest state, often remain unchanged for many months, and have all the appeai'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 sim (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 distin- 
guished because of their minuteness, yet the light they reflect is golden in character, 
and seen to be abundant in proportion to the quantity of sohd gold present. Portions 
of fluid so dilute as to show 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. A^Tien the 
preparation is deep in tint, then common observation by reflected light shows the 
suspended particles, for they produce a turbidness and degree of opacity which is suffi- 
ciently 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 sho-wn 
by the deposit which occurs when they are left at rest. If the gold be comparatively 
abundant, a part wiU soon settle, i. e. in twenty-four or forty-eight hours ; but if the pre- 
