Manufacturer and builder 9 / 1871
When speaking of the so-called Neuwider green, it was mentioned that, by its manufacture, liquids are left which still contain free arsenious acid, acetic acid, and dissolved Schwenfürter green. In case the latter is made from blue vitriol and acetate of soda, after one of the methods described by us, then the liquids left contain sulphate of soda, which is formed by the sulphuric acid of the blue vitriol combining with the soda, while its acetic acid combines with the copper oxide of the blue vitriol to verdigris or acetate of copper. The sulphate of soda remains then passive in the liquid, and the paint combines with only a portion of the acetic and arsenious acids. These remaining liquids being a diluted arsenious vinegar, are therefore easily utilized in the manufacture of successive greens.
A remnant solution from 100 pounds verdigris may be considered as still containing two thirds of the vinegar, besides some 20 pounds of arsenious acid, and the remnant solution of acetate of soda made from 165 pounds sulphate of soda, and 40 pounds of acetic acid or acetate of soda, and used for the manufacture of Schweinfürter green, contains one third, or 20 pounds, of the acetic acid, and also 20 pounds of arsenious acid, both solutions being consequently very poisonous.
All these arsenious copper paints require great care in manufatcure, on account of the arsenic used; and this is especially the case with the Neuwider and other greens, in which large quantities of this substance are manufactured. This arsenious acid may be obtained in the trade, either in lumps or in powder; in the former state, it is more sure to be free of sulteration, and therefore preferred by some. It is prepared for use by pulverization in large iron mortars. In order to protect the workman from the fatally poisonous dust, it should be pulverized under water, and afterward groud in a mill, the same precaution being observed.
Personal Precautions.
Every workman in this branch of business should keep himself scrupulously clean. Neither the dust of the arsenic nor the green paint should be allowed to remain on his clothes. It has a tendency to adhere to the skin of the hands, and especially to stick below and around the nails; therefore the hands must not touch any more sensitive part of the body before scrupulous cleaning. They should not be kept longer in the arsenious solutions than is absolutely necessary, as otherwise the laborer is soon attacked by the arsenic disease. Unfortunately, the contact with the liquids, and the dust in sifting and packing, can not be totally avoided. The influence of the vapors developed by the boiling arsenious solutions is greatly removed by placing the boilers in well-ventilated buildings, with proper arrangements to cause the fumes to ascend rapidly out of harm's way; nut in spite of every precaution, in the course of time the laborers are bound to suffer.
Arsenic Disease.
Thus far no remedy has bee ndiscovered to prevent the final attact of the peculiar disease caused by the external exposure of the body to arsenic. It commences with a burning sensation between the thighs, the lower abdomen, and genitals. Suppurating ulcers appear there, and afterward the same symptons show themselves around the nostrils. As soon as this is the case, the laborer must be removed from work, when in three to four weeks the sores will heal without leaving any injurous results whatsoever; the healing power of nature drives out the injurous substances by suppuration, and therefore should not be interfered with, but as much as possible promoted. As soon as the cause of the ulcers is removed, they heal by themselves, and must not be interfered with by plasters or so-called healing salves.
In case the laborers are not at once removed from the works as soon as the symptoms described show themselves, they soon grow worse, so much so that in two or three weeks they are unable to walk, when it will take several months to insure their recovery, which often becomes doubtful, especially when their systems are undermined with the habitual use of tobacco or strong drink.
For this reason, in all well-regulated factories the laborers are periodically removed from this branch of the business, as soon as the first symptom shows itself, and then no further inconvenience is experienced. After four or five weeks, they may resume the same kind of labor.
The copper paints are likewise very poisonous, especially those containing the most arsenic. There are scores of instances where injurious effects resulted, not only from such paints entering the stomach, but from external contact. We will only mention one of our experiencs. Many years ago, we wore in the chemical laboratory a cap similar to so-called smoking-caps; it was internally lined with a strip of green leather, which touched hair and forehead. In a short time some very sore suppurating pimples showed themselves; the cap was suspected and abandoned, when they healed in a short time. In order to experiment, the cap was again used, when the same symptoms showed themselves. It was thus considered sure that the cap was the cause. a piece of the leather being chemically tested, showed the presence of arsenic, proving that it had been colored with one of the pigments described, (the arseniate of copper kind.)
All these arseniate of copper greens are used as oil and water.colors; it is, however, somewhat difficult to rub them very fine, and as oil-colors they are deficient in body and do not cover very well; in this respect they are inferior to the different kinds of chrome greens. However, they have the advantage over the latter of withstanding in a greater degree the influence of air and light; on fresh lime they can not be used, as the caustic lime withdraws the acetic acid, and a yellowish green arseniate of copper remains which has a disagreeable color. Sulphurous vapors also act injuriously, as they change the green to a brown tint.
With this paper our series of articles on the paints made of copper is concluded.
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