After the galena is dissolved by the nitric acid, and the sulphide of lead is changed into liquid plumbic nitrate, then the sulphur which floats occasionally on the surface of the solution is removed, and the substance which remains undissolved is washed out and is also removed. The liquid nitrate is then passed through filters of felt, linen, hemp, flannel, &c., or is left standing for about 12 to 18 hours for settling and clearing. Now in order to produce the chrome yellow from this nitrate of lead, bichromate of potash is dissolved in water, and a sufficient quantity of this solution is poured into the plumbic nitrate solution until all the plumbic nitrate is changed into chromate of lead, called “chrome yellow.” Instead of the bichromate of potash, neutral chromate, or chromate of soda may be used, and for the purpose of obtaining lighter tints they may be tempered with sulphuric acid or any other compound of sulphur. The liquid nitrate of lead is placed, preferably, in large open receptacles of wood, clay, earthenware, or other suitable material, and the chromate of potash solution is put into similar vessels, and then placed above the receptacles containing the plumbic nitrate. The chromate of potash can then easily be run into the lower receptacles containing the liquid nitrate of lead, and this mixture is constantly agitated by similar means until all the plumbic nitrate is changed into chromate of lead, which is precipitated on the bottom of the larger receptacles. The chemical action which takes place by this changing of nitrate of lead into chromate of lead is that the chromic acid of the potash assumes the place of the nitric acid, which parts from the lead and combines with the potassium, so that the lead as chromate of lead is precipitated on the bottom of the receptacle, while the nitric acid of the plumbic nitrate remains with the potassium, which latter has parted with its chromic acid, and a quantity of water as solution above the chromate of lead. To change the nitrate of lead recovered out of the 100 lb. of galena above mentioned into chromate of lead, about 56 lb. of bichromate of potash are used. This change usually takes place in from about 10 to 30 minutes, after which the chrome yellow (chromate of lead) is left for a few hours to settle, and then the solution standing on top of the chrome yellow is drawn off by suitable means, or run out of the vessel by opening a cock placed above the level of the chromate of lead. The latter is then washed by adding pure water, which is poured upon the chrome yellow, and the mixture is stirred up, so that all the remaining liquid nitrate of potash is removed. After this is accomplished, the mass is left to settle, and the water is again drawn off from the precipitate, which then settles on the bottom of the receptacle. This washing is repeated as often as is deemed necessary.