Scientific American 40, 22.6.1850
THE MINING OF CHROME. - A Growing Trade. - We are gratified to learn that the diggers of chrome, in Delaware county, are as busy as the gold diggers in California. One firm has upwards of one hundred hands employed, and are daily shipping the mineral to Baltimore. The proprietors of farms upon which it is found, receive three dollars per ton for washed chrome - and in the rock state it is sometimes worth five dollars per ton. The mineral is found in gread abundance, at various points east of the Mine Ridge, in Lancashire, Chester and Delaware counties, and is all, or nearly all, shipped to Baltimore.
Chrome is not found in the metallic state; its oxyde is a green ochry substance which is generally intermixed with siliceous minerals. Chromic iron (which is the kind above alluded to) is dought after to obtain from it the chromic acid, for the preparation of the beautiful chrome yellow used in painting and dying. It is found tn the Shetland Islands, in Styria, in some part of France, and elsewhere; but is is more pelntiful in the region above mentioned than in any other place we have ever heard of.
Chromate of lead i the same substance as the chrome yellow artificially prepared. When crystalized, its color is of a deep red orange, and when powdered, orange yellow.
[The above is from the Miners' Journal, Pottsville. It is not over thirty years ago, we believe, since a vessel from Baltimore arrived in the river Clyde with a considerable quantity of chrome ore for ballast, which was considered of no more use than common cobble stones. At that time there was only one man in the city of Glasgow who knew its value, and he immediately bought up the ballast for a small consideration, made it into the bichromate of potash, and introduced the beautiful chrome yellow into the cotton printing and dying. The discovery was first made in France, and introduced by the same gentleman, himself a Frenxhman, into Scotland. We will now describe some of the applications of chrome, as employed in the arts:
Chrome Paint. - To make chrome paint, the bichromate of potash is dissolvent in water, and the rate of four parts, (ounces or pounds,) and to that is added three parts by weight of the acetate of lead. This makes a beautiful light yellow precipitate, as the chromic acid leaces the potash and combined with the lead. This is left to settle for some time, when the clear is poured off, and some clean water poured in, then left to settle, and the residue dried. It is afterwards ground and kept in tin vessels to be mixed with oil for house painting, or made into cakes with glue for draughtsmen. It is never used by skilful portrait painters, as it acquires a greenish hue by age. This is very beautiful yellow for house and coach painting.
Chrome Yellow Dye. - Chrome is now used in the woolen dyeing very extensively, for coloring black. It is only a few years since its qualities for this purpose were discovered. We will however only describe its application to cotton. To ten pounds of yarn or cloth, which must be clean and have been boiled, 3 ounces of the bichromate of potash is dissolved and put in one vessel, and 9 ounces of sugar of lead in another - these vessels having as much water in them as will allow the cotton goods to be handled freely therein. They are first well handled in the lead solution for about eight minutes, then squeezed, shaken well out, and handled in the chrome liquor for about the same lenght of time. They are then squeezed out, dried, and run through the first lead solution, then washed in water and dried. With a greater amount of stuff, and handling the goods so as to give them two or three courses, a deeper color will be produced. If the nitrate of lead is used in the place of acetate, a redish yellow is produced. This is a most beautiful yellow. If lime is used along with the lead, a faster color is the result; but great care must be exercised to finish it in clean water, in which is some weak muriatic acid, and then was it well.
Chrome Orange. - For 10 pounds of cotton use 1 lb. 2 oz. of chrome, 2 lbs. brown sugar of lead, and 1 lb. of litharge. Boil the lead, and use a little lime amongst it; then dye in the same way as the yellow, only giving two dips, and using the stuff up at the two separate handlings. The goods should always be well aired out of the chrome; and for the orange, at the last fip, after the cotton has got the chrome, a vessel of clean lime water heated to 206° is kept ready, and the goods run through it, when they at once assume a beautidul orange color. Before they get the lime liquor, they look bad, striped, and brownish; but no sooner do they get the hot lime, than they look rich and evenly. These colors are easily dyed, and these receipts may be of use to many in the cotton region, who do considerable at domestic dying.
Green in cotton is also dyed, by first dyeing it blue with indigo, washing it, and then dyeing it a chrome yellow on the top of the blue.