The Manufacturer and Builder (9 tai 10), 1877
We read in the Cumberland Alleghanian that the water from the mines above Cumberland is impregnated with sulphate of iron, the result of the oxidation of sulphuret of iron in the coal, and flows into Will's Creek. The report goes on to say "The creek is now very low and but a very small body of water flows down its bed. At the head of the city are two extensive tanneries, and in the tanning of hides large quantities of tannic and gallic acids are poured into the stream. As soon as these acids come in contact with the sulphate of iron the water becomes black, as is now the case in front of our city. There are millions of gallons of ink now lying in the bed of the creek, which needs but bottling and packing to make a salable article for exportation."
We may add to this that the appearance of iron sulphate in springs near coal mines is very common. We noticed several such cases near Mauch Chunk; the least trace of tannic or gallic acid will color the water black.
In this connection we may mention an interesting and instructive lecture-room experiment which we used to give to classes in chemistry, in order to, show how the reaction of these substances can be used as a test. A little dust from a paved city street, where horses with iron shoes and carriages with iron wheels are continually passing - for instance, dust off Broadway, New York, or from a street much used for railroad traffic, such as the Bowery, must contain considerable iron. Some of this dust is placed in a test tube and a few drops of nitric acid added, then water, after which it is allowed to settle. Next dust is taken that collects on the floor of a ball-room after a ball has taken place; this dust is mostly the result of the wearing out of the shoe soles, which necessarily must contain, with the leather ingredients, tannin, which transforms gelatin into leather. If now some of the solution of the Broadway dust is added to the ball-room dust, an ink will be formed, showing what the prevailing ingredients are in these two kinds of dust.