A NEW PROCESS OF WHITE-LEAD MANUFACTURE.
In two former articles (June 16 and November 10, 1883) we noticed the dangers to life and health which accompany the manufacture of white-lead as at present carried on, and we reviewed the several attempts made to find a substitute. We are still of opinion that such substitutes will prove effectual in their measure; but we cannot shut our eyes to the fact that the enormous production and consumption of ordinary white-lead must nevertheless continue, chiefly on account of its cheapness, for its enduring qualities, and for its capability for purposes in jointing, calking, machinery and hydraulic use, which other substances fail to fulfil. In these circumstances it is interesting to know that almost coincident with the Report of Mr Redgrave, C.B., Her Majesty’s chief Inspector of Factories—to which we alluded in a former article (June 16), and which so forcibly shows the evils under the old ‘stack’ process of white-lead manufacture, as usually carried on—there has been discovered, and brought into full operation, a process by which white-lead of the purest and best quality is produced in one-sixth the time, and at considerably less cost than under the old process. The necessity for the work of women is also avoided, and the operatives completely secured from contact with the dangerous white-lead dust.
It may help our readers to an understanding of the subject if we quote first a brief description of the ‘stack’ process, from a previous Report by Mr Redgrave: ‘The lead is received in “pigs.” These are melted in a furnace, and then cast in water or in moulds of various forms best suited for the action of the acetic acid. The acid is placed in pots of earthenware, on which the moulded lead is placed; and the pots are then arranged in large chambers, called “stacks,” and covered with tan. Row after row of pots and tan are placed one above the other, until the stack is full, in which condition the stack remains for about three months. Carbonic acid gas is evolved during this time, escaping through the ventilators, and causes the deposit of white-lead on the moulds of lead. If the above were the only process, it would be comparatively innocuous; but it is the work that succeeds from which the evil of lead-poisoning arises. The tan is carefully removed from layer after layer; white-lead is found caked upon the moulds of lead; but a very little motion causes it to break up into powder. The lead, loaded with this deposit, is then carried in trays, and emptied into cisterns of water, through which, by agitation, the white-lead passes to the grinding-mills, and the blue lead is raked out of the cisterns for further use. After being ground in the wet state, the material is placed in pans and carried into the ovens to be dried; it is then carried from the ovens to the warehouse, to be packed in barrels. Such are the principal processes in which females are employed, and which are most prolific of disease and death. The injuries to health arise from the external contact with the skin of the white-lead, whether in the dry or moist condition, and the inhalation of the dust or powder into the lungs, or its being imbibed into the stomach through the mouth. As for the prevention, external or internal, no means have yet been discovered by which this could be attained. The mitigation of the evil lies in excessive and enforced cleanliness, with the use of special clothing and appliances when at work.’
When, however, the testimony given in Mr Redgrave’s later Report is considered, it will be seen that the ‘excessive and enforced cleanliness, with the use of special clothing and appliances,’ fail to accomplish their object, the chief reason being, as testified by one sufferer: ‘The air of the factory was always full of white-lead dust.’ Another, speaking of her clothes, said: ‘Dust came from them like a miller, and used nearly to choke me.’ And managers of factories state to Mr Redgrave: ‘Respirators are provided, but work-people as a rule will not wear them. The respirators are troublesome.’ The fact is, there is this dilemma: without the respirators, lungs and stomach get filled with the dangerous white-lead dust; with the respirators, the perspiring, half-choked women cannot work. The problem really is how to produce white-lead without raising this poisonous dust, as it is well known that the grinding in oil is with any ordinary care perfectly innocuous. The very stringent legislation lately authorised does not touch this point.
Attempts have been made to produce white-lead by precipitation, and thus to avoid some of the dangers; but the product is an inferior one, being composed of minute crystals which will not blend with the oil, and are deficient in the most important qualities necessary for paint, and for the other purposes for which true white-lead is largely used. The precipitated lead has also to be washed and stored, as the white-lead from the stack process.
Happily, just at this juncture a simple but wonderful process has been discovered, perfected and patented by Professor E. V. Gardner, of 44 Berners Street, London, W., for many years Director of the Scientific Department, and Professor of Chemistry to the Royal Polytechnic Institution, and who marches with the age in the application of the wonderful power of electricity to this branch of manufacture. He avails himself to the full of that great representative of all energy in forming what is called a galvano-electric combination in the process of manufacture of white-lead, as follows:
The metallic lead, cast into the form of gratings, and bent into narrow arches, is closely ranged in order upon wooden trays covered with pure sheet-tin—the most practically useful electro-negative to be had. Dipped by mechanical contrivance into a certain acid mixture, to give a chemically clean surface, and to promote the after-process of corrosion, they are placed in chambers built of brick, from twelve feet square and upwards, having a glass roof and windows for observation, and having a floor of the electro-negative and highly electro-conductive tin heated from beneath by steam to the necessary temperature of about one hundred and twenty degrees Fahrenheit. These chambers may each contain as small a quantity as from eight to ten tons of lead, and range up to eight hundred or a thousand tons. Gases, composed of a mixture of acetic acid vapour and atmospheric air at a similar temperature, are introduced by stoneware pipes from an ingenious apparatus where they are generated; and passing through holes in the pipes a few inches from the tin-covered floor of the chamber, they pass upward, and permeating the whole chamber, electric action commences. At the end of the second day, there is a beautifully white surface. On the third day, carbonic acid vapour is introduced by the same means, hastening still more the formation of white-lead. This goes on for two weeks, at the close of which time, so active has been the action of the substances engaged, by reason of the electrical energy, that there is more white-lead formed than under three months’ working of the same amount of lead by the old process. The gases are then shut off, the chamber cooled, ventilated, opened, and the contents withdrawn, the trays being emptied through a special hopper into the ‘agitator,’ a horizontal cage of round iron bars revolving in a closed case. After being rotated a few minutes, the whole of the white-lead is disengaged, and falls into a pit underneath, leaving the cores that have not been converted in the cage, from which they are collected and remelted for further use. From the pit, the white-lead is conveyed to the mill by an endless band, on which are fixed a number of small buckets, which, filling themselves with the white-lead as they pass through the pit at the bottom, discharge it into the mill as they turn over at the top, whence, after passing through the crushing-rollers, the white-lead falls into the mixer, and issues forth, when combined with oil, in the shape of white-lead of one unfailing quality, being of perfect character as to body and testing powers, and of the purest colour.
The work is continuous from first to last. As all the apparatus is carefully closed in, there is no dust, nor do the hands of the operatives once touch the material. The Sanitary Record (October 1883) says: ‘Professor Gardner has completely revolutionised the manufacture of white-lead. Not only has he rendered it a comparatively innocuous industry, but he has made it a much simpler process, and reduced the time hitherto required for its production in an extraordinary manner, and so facilitated its rapid make, and at a much lessened cost of production. But these great advantages of the process sink into insignificance when compared with its hygienic working in rescuing hundreds of poor creatures from lingering illness, not taking into account the attendant expense of their treatment and support, which falls on various local authorities.’
Mr Redgrave, having carefully inspected the working of the process, has written to Professor Gardner as follows: ‘I think it right to state that having carefully inspected your works at the bottom of Rolt Street, Deptford, it appears to me that the process of the manufacture of white-lead there is free from nearly all the objections on the score of exposure of the persons employed to the injurious effects, hitherto deemed to be inseparable from the occupation. The material and the product are alike isolated, there is an absence of dust, and handling or manipulating is unnecessary.’
As the white-lead manufacturers of our country are not only an influential and wealthy body, alive to their own interest, but also most anxious for the welfare of their operatives, they must hail this new process with much interest, and adopt it gladly. The general public will rejoice to be assured that the valuable and useful white-lead is no longer prepared at the cost of life and health to many, especially women, as has hitherto been the case.