When the plates are thin enough, make them red hot once more, and cut them into small bits with a pair of sheers. Put these bits into a tall, narrow-mouthed cucurbit, and pour on them twice their weight of good _Aqua regis_, made of one part Sal Ammoniac, or Spirit of Salt, and four parts Spirit of Nitre. Set the cucurbit in a sand-bath moderately heated, stopping its orifice slightly with a paper coffin, to prevent any dirt from falling in. The _Aqua regis_ will presently begin to smoke. Round the little bits of Gold will be formed an infinite number of small bubbles, which will rise to the surface of the liquor. The Gold will totally dissolve, if it be pure, and the solution will be of a beautiful yellow colour: if the Gold be alloyed with a small quantity of Silver, the latter will remain at the bottom of the vessel in the form of a white powder. If the Gold be alloyed with much Silver, when the Gold is dissolved the Silver will retain the form of the little metalline plates put into the vessel. When the dissolution is completed, gently pour off the liquor into another low, wide-mouthed, glass cucurbit, taking care that none of the Silver, which lies at the bottom in the form of a powder, escape with the liquor. On this powder of Silver pour as much fresh _Aqua regis_ as will cover it entirely; and repeat this till you are sure that nothing more can be taken up by it. Lastly, having decanted the _Aqua regis_ from the Silver, wash the Silver with a little Spirit of Salt weakened with water, and add this Spirit of Salt to the _Aqua regis_ in which your Gold is dissolved. Then to the body containing these liquors fit a head and a receiver, and distil with a gentle heat, till the matter contained in the cucurbit become dry. _OBSERVATIONS._ It is certain that _aqua regis_ is the true solvent of Gold, and that it does not touch Silver: so that if the Gold dissolved in it were alloyed with Silver, which is often the case, the two metals would by this means be pretty accurately separated from each other. But if you desire to obtain from this solution a Gold absolutely pure, you must free it, before you dissolve it, from every other metallic substance but Silver; because _aqua regis_ acts upon most of the other metals and the semi-metals. We shall shew under the head of Silver, as we promised before, how to purify a mass of Gold and Silver from every other metallic alloy. Thither also we refer the common parting assay performed by means of _aqua fortis_: because in that operation the Silver is dissolved, and not the Gold.