The London Journal of Arts, Sciences, and Manufactures, and Repertory of Patent Inventions.
Conducted by Mr. W. Newton, of the Office for Patents, Chancery Lane. (Assisted by several Scientific Gentlemen.)
VOL. XXXVI. (Conjoined Series.)
London: Published by W. Newton, at the office for patents, 66, Chancerylane, and Manchester; t. and W. Piper, Paternoster Row; Simpkin, Marshall, and Co., Stationers' Court; J. McCombe, Buchanan St., Glasgow; and Galinani's Library, Rue Vivienne,
Paris. 1850
No. CCXX.By M. Combes.
[Translated for the London Journal of Arts and Sciences.]
The maladies to which manufacturers of white lead, as well as those who are engaged in preparing or using pigments or other preparations having lead for their base, are peculiarly liable, have for a considerable period excited the attention of scientific men, and particularly that department of the government having the public health more especially under its care.
It is well known that, in 1783, Guyton Morveau proposed to substitute zinc white for white lead in the preparation of pigments; but all attempts made for that purpose, from that period to the present time, have in great part failed, either from the high price of the zinc white, or from other causes, which form no part of the subject under discussion in this report. M. Leclaire recently undertook the manufacture of oxide of zinc on a large scale, in order to apply it to painting vessels and to other purposes.
On that occasion statistical documents, extending over a considerable period, and collected from the hospitals of Paris by the Council of Health of the Department of the Seine, touching the maladies under which workmen using lead or preparations of lead suffer, were very extensively circulated. From these documents we learn that, during a period of ten years (i.e. from 1838 to 1847 inclusive), the hospitals received 3,142 patients, of which number 1,898 came from two manufactories of ceruse or minium, in the Department of the Seine. MM. Theodore Lefebvre&Co., and Poelmann Brothers, manufacturers of ceruse on a very large scale, in the environs of Lille, struck with the injurious effect it must necessarily have upon their business, addressed to the Academy certificates from medical men, and a report from the central Committee of Health, in the Department du Nord, stating that, in consequence of the improvements made in the process of manufacture, and the attention paid to the health of their workmen (150 in number), none of them had been attacked with cholic for upwards of a year. MM. Lefebvre and Poelmann concluded, by requesting the Academy to verify the facts by means of a Commission, to be appointed for that purpose.
In order to carry out this object MM. Lefebvre and Poelmann' s manufactory was visited, and also the white lead manufactories in the Department of the Seine, and all those in the environs of Lille, one only excepted. From the information thus gathered we shall shew the various improvements introduced into many of these establishments, and at the same time point out what is further requisite. We generalize our observations, leaving to the proper authorities the task of prescribing to each manufactory the improvements necessary for the health of the workmen, persuaded, as we are, that a sense of humanity will prompt the manufacturers to anticipate any orders to that effect.
White lead is generally manufactured in France by what is called the Dutch process; in a manufactory at Clichy, however, the French process (established by M. Roard, according to the instruction of M. Thenard), is partially used, for the purpose of improving the carrying on of a portion of the manufacture which it is very difficult to deprive of its injurious effects, viz., the preparation of oxide of lead or massicot in reverberatory furnaces. A very strong draft even is insufficient to protect the workman against the plumbic vapors; as they are constantly occupied in stirring or raking the oxide of lead formed, in order to lay bare the surface of the metallic bath. The succeeding operations, up to the potting of the white lead, are innoxious,—being performed by the wet method. The processes of drying and pulverizing the cakes of white lead are common to all modes of manufacture.
The Dutch process comprises the following operations: — 1 st. Fusion, and casting of the lead into plates of any required thick ness, or into bars of a long rectangular form. 2nd. Laying the lead in alternate layers with dung or tan. The lead is placed upon pots containing dilute acetic acid. It remains in the chambers thus filled for from thirty-five to forty days when dung is used, or from sixty to ninety if tan be employed. 3rd. The layers of lead (converted for the most part into carbonate) are now successively uncovered, and the white lead formed is removed from the metallic lead; after which, the white lead is ground and sifted, in order to remove any portions of metallic lead which may be mixed with it. 4th. Grinding up the white lead with water. 5th. Moulding and drying. 6th. Pulverization and dry-grinding of the cakes of white lead; sifting, and packing into casks, the white lead intended to be sold in the state of powder. 7th. For white lead which is intended to be sold in the state of paste, mixed with oil,—mixing the powder produced by the dry-grinding (without previous sifting) with from 7 to 10 per cent. of its weight of oil. The mixture is effected in a close vessel, by means of an agitator; after which it is passed through several pairs of cast-iron rollers. The fine homogeneous paste, thus produced, is received in a vessel containing water, from which it is taken and put into casks for sale.
lst. The melting of the lead.—This is performed in a cast-iron vessel, and no hurtful vapors are produced unless old lead be introduced, which has been used in previous operations, and is therefore covered with a layer of carbonate. In well-conducted establishments the melting vessel is placed under a flue or funnel, in communication with the chimney of the furnace, or any other chimney having a good draft. The platform of the furnace is connected with the flue or funnel by means of an outer casing of iron, of any convenient shape, and having doors or openings for the purpose of supplying the lead to be melted, or running the melted metal into moulds. These precautions appear to us to be sufficient to protect the workmen from injurious vapors. Besides, the melting of the lead is only effected at very long intervals.
2nd. The placing of the sheets or bars of lead in alternate layers with dung or tan.—From this operation the workman is not in the least exposed to injury. In all the French manufactories, one only excepted, the lead is cast in sheets; and in each of the pots containing acetic acid is placed a thin sheet, rolled in a spiral form, and bearing upon two supports near the bottom of the vessel. In one of the manufactories in the Department of the Seine, the lead is cast into bars, which are placed in beds, upon pots of less depth than those generally employed, and which do not contain rolled lead.
3rd. The separation of the carbonate from the metallic lead, and the pulverization and sifting of the same.—These operations constitute the most injurious part of the manufacture. In all the establishments which we visited, with the exception of one, these operations were performed as follows: —The workman first detaches the large scales or crust of white lead, which adhere very lightly to the metallic lead; he then takes in his hands the sheets of lead covered with ceruse, unrolls those which were placed in the pots, twists them about in various directions, and puts on one side the detached scales. This operation, which is called picking (epluchage) in the Department du Nord, is sometimes performed in the place where the layers are formed, and sometimes in another, into which the sheets covered with white lead are carried, just as they come from the beds. The picking operation, in which the operator has his hands constantly covered with carbonate of lead, is not, however, the most unhealthy part of the manufacture, as the white lead is detached in thick scales, which produce very little dust; but the sheets of lead are still partially covered with some portions of white lead, which adhere very firmly.
The old method of detaching these was by placing a pile of the sheets of lead upon a slab of stone, and striking the lead with a wooden beater; by this means the white lead was caused, either to fall off in the shape of minute scales, or else it rose in the shape of dust into the air, and was respired by the operator. This operation, which is still carried on after the old method in some establishments, is called scouring (decapaye) in the Department du Nord; but when so conducted, is extremely injurious to health. The scouring operation is now, in mauy manufactories, performed by mechanical means, which render it much less injurious than heretofore. The sheets, covered with adherent white lead, are carried in a hand-barrow to the scouring machine, and the operator takes them, one by one, and lays them carefully on a travelling endless-cloth, by which they are carried to the top of an inclined plane, down which they slide to an arrangement of apparatus, consisting of two pairs of longitudinally-grooved pressing- rollers, beyond which an inclined sieve is situated. Between these rollers the sheets of lead are made to pass, in order to detach the white lead therefrom. When the sheets of lead have arrived at the lower part of the sieve, they are received into a wagon, and pass away into a contiguous chamber. The white lead, which is detached from the sheets of lead, falls from the rollers upon a travelling-cloth, and is conducted to a hopper, together with the white lead which falls from the sieve; and the whole is delivered by the hopper into a wagon, placed in a chamber having closed doors. All the parts of the apparatus are en closed in wooden cases, which are kept shut during the working; there being but one opening, viz., that for allowing of the operation of the endless cloth, which feeds in the lead. The wagon containing the white lead is run out of the chamber as soon as the operation is completed and the dust has ceased to fly about; and its contents are added to the products of the picking operation, in order to be submitted to dry-grinding. This latter operation is mostly performed with vertical stones, turning in horizontal troughs. The white lead, when ground, is poured into the hopper of a fine bolting-cylinder, enclosed in a casing; into which the powder falls after passing through the meshes of the bolting-cylinder. Any scales of lead which may also have passed through the stones, will fall to the bottom of the bolting-cylinder, and from thence into a separate receptacle. The white lead, thus sifted, is mixed with water, and again ground.
In several manufactories in the environs of Lille, the pulveriza tion of the scales is effected by means of several pairs of horizontal cylinders, fluted in a direction transverse to their axes. The substance ground falls on to one or more metallic sieves; after passing through which, it is conducted by hoppers into a chamber, supplied with several jets of water. The scales of lead which cannot pass through the sieves fall into another chamber. The whole apparatus, consisting of grinding-cylinders and sieves, occupies the height of one story, and is enclosed in a wooden casing, furnished with a hopper above, which is kept full of scales of white lead, in order to prevent the dust from rising: the hopper may, if thought desirable, be closed by a trap. This arrangement constitutes one of the most important sanitary improvements upon the old system of manufacture.
In the manufactories of the Department of the Seine, in which the lead is cast in bars, instead of being operated upon in rolled sheets, the picking, scouring, pulverizing, and sifting operations are performed mechanically, by means of successive apparatus, enclosed in one casing, and divided into several compartments, connected together by wooden channels.
The first compartment or chamber contains three pairs of fluted rollers, which effect the picking and scouring of the bars; and also three other pairs, which effect the grinding of the scales. There are two openings at opposite sides of this chamber; one of which admits the endless-cloth, upon which the bars incrusted with white lead are fed in; and the other, through which the bars, after being cleansed, make their exit by sliding down an in clined plane of perforated sheet-iron, which is shaken at intervals by suitable mechanism. On leaving this compartment, they are straightened by beating with a wooden beater, and sorted; those which are fit for use again are selected and put aside; while those bars which are in great part decomposed, are melted and re-cast. The scales, on being detached by the action of the three pairs of fluted rollers, between which the bars successively pass, fall upon a moveable endless-cloth, extending under the cylinders, and also under the perforated iron plate; this cloth feeds the scales of white lead to three pairs of plain rollers, by which they are ground. The powder falls upon an inclined plane, and from thence into a casing, where it is received into vessels, attached to an endless band, and carried thence to the upper part of a second chamber, united to the first by the wooden channel, in which the endless-band, carrying the buckets, works. This second chamber contains the bolting-cylinder for sifting the white lead, and separating it from any scales of metallic lead which may have become intermixed with it: these latter are conducted into a separate com partment. The white lead falls to the bottom of the chamber, from whence it is afterwards taken (when the operation is completed and the dust has ceased to fly) and ground with water. In the operation just described, the workmen who receive the bars of lead, on their leaving the chamber, are still exposed to the injurious influence of the white lead powder; they are therefore made to work at this dangerous post by turns—each man being thereby prevented from working consecutive days.
The separation of the scales of white lead from the metallic lead, and the grinding and sifting of the same in a dry state, cannot be considered as salubrious operations under any circumstances; notwithstanding the important improvements which have been made upon the old methods, and the sanitary precautions taken in most of the establishments visited. Thus, the picking by hand of the scales of white lead from the metal, is attended with a certain degree of danger; attempts to obviate which have been made by several manufacturers, by causing the workmen to wear gloves. This precaution is, however, not merely insufficient, but it is attended with disadvantage, as the work cannot be so well performed as by the bare hand.
In the only establishment in which the picking is not manually performed, the bars of lead, on coming from the chamber, after passing through the rollers, still retain some portions of carbonate of lead, which are reduced to fine powder when the bars are beaten straight. This fine powdered white lead escapes from the chamber containing the grinding apparatus, either through the openings made purposely for the passage of the different substances, or through the holes in which the shafts of the mechanism work. All, or nearly all, insalubrity would be avoided in this manufac ture, if the separation of the scales of white lead, the pulverization, and the sifting, were performed under water; or, at least, if the ceruse and the residue of lead, on coming from the space occupied by the grinding apparatus, were received upon gratings or sieves, supplied with a number of minute streams of water, by directing a current of water through a perforated plate. According to the information furnished by M. le Play this would appear to be the mode of operation followed in England, where the residues of lead are again melted before being replaced in layers with the tan. We would call the special attention of manufacturers of white lead, and the government, to the importance of a method, the introduction of which appears to be attended with many ad vantages and but few difficulties; this is apparent from its being generally employed in England. The white lead would, by this means, undergo a washing, which would carry off, at least partially, the soluble salts by which its purity is injured; it is moreover necessary to dilute it with water, to submit it to the following operation
4th. Grinding the tohite lead with water.—The white lead is placed in tubs, and diluted with water, so as to form a soft paste. It is then passed successively through a series of horizontal stones, by which its trituration is completed. This grinding with water is perfectly innocuous. The workmen do not touch the paste with their hands; they merely pour it into the hoppers above by means of ladles.
5th. Moulding and desiccation of the white lead paste after being ground with water.—In all the manufactories, one only excepted, the soft paste is poured into earthen vessels of a conical form, which are exposed to the action of the air in a drying apparatus. By this means, a large portion of the water is evaporated; —the white lead acquires a certain consistence, and undergoes a contraction, by which it is detached from the sides of the earthen pots, and may be easily removed. The desiccation is then completed in a proper drying stove, by means of a current of hot air. The sides of the pots become covered with a layer of white lead, which is ordinarily removed with an iron scraper. This operation is performed by women or children, and is attended with inconveniences, which are sometimes obviated by cleaning the pots with water; this, however, occasions additional expense and difficulty, which may prevent its general adoption. A portion of the white lead is introduced into commerce, after drying, in the form of cakes, which are wrapped in paper, and carefully packed in casks, so as to avoid breaking them as much as possible. The handling of the cakes of white lead cannot be considered to be free from inconvenience, although unattended with danger, if due precaution be observed. In one manufactory in the Department of the Seine, the white lead is not potted as above mentioned. The soft paste is poured from the vats on to a cloth, in which it is wrapped, so as to form a square flat packet. Several of these packets, being arranged in alternate layers, with corresponding pieces of wood, are submitted to the action of a hydraulic press; and, by this means, the water is, in great part, expressed. The cakes are then uncovered, and cut into convenient shapes for the drying apparatus; from whence they are carried to the stove. A small portion of the products of this manufactory is sold in dry cakes; but the same care is not taken in packing these in casks as the conical cakes; for the product is disposed of to parties who are well aware that form is no indication of quality. The cakes are simply thrown into the cask, and packed by means of a cylinder, worked by a hydraulic press.
6th. Grinding and sifting the white lead preparatory to send ing it to market. —This second pulverization is generally effected by means of vertical mill-stones, revolving in horizontal troughs of the same material. The ground white lead is shovelled into a hopper, leading to a silk bolting cylinder, enclosed in a casing; at the bottom of which the white lead falls in the form of a fine powder. That portion which cannot pass through the silk, falls into a separate case; from which it is taken to be again passed through the mill. When the dust has ceased to fly, the sifted white lead is packed tightly in casks.
According to the above plan, the operations of pulverization, sifting, and packing, are evidently very injurious, by reason of the dust which flies about. The injurious influence may be much lessened by enclosing both the mill-stones and the bolter which receives the ground white lead immediately therefrom in an air-tight case. This has been done in one manufactory in the environs of Lille,— horizontal stones of white marble being substituted for the ordinary vertical stones. Each pair of stones is enclosed in a drum, furnished with a hopper above, in which the cakes of white lead are placed, and undergo a preliminary breaking by means of a striated cone, placed in its interior, and revolving on its axis. The fragments fall from thence into a hopper, fixed above the upper or running stone. The powder ground is thrown out by centrifugal force towards the periphery, where it is received by two openings and conducted to the bolter, which is in a lower chamber, and closed by a double door. In order to avoid the flying of dust during the packing in casks, the white lead is poured carefully into the cask, and packed by means of a pressing-screw, which works a cylindrical plate, a little smaller in diameter than the barrel, and presses it down upon the white lead.
7th. State of the white lead when gold in the market. —In the environs of Lille nearly the whole of the products of the white lead manufactories are sent out in powder or in cakes, viz., about two-thirds in powder and a third in cakes. A manufacturer in the Department of the Seine has set up in his establishment a complete workshop for grinding the white lead with oil; and nearly seven-eighths of his products are sold in the state of paste, containing from 7 to 9 per cent. of oil. In this manufactory the cakes of white lead are ground after desiccation in a mill similar in construction to a coffee-mill, and set in a closed chamber,— the white lead being first coarsely pulverized. When the dust has ceased to fly, the powder is to be poured gently into an iron cylinder, placed horizontally,—a small quantity of oil being added. The cylindrical vessel is then closed, and the mixture is effected by beaters, fixed upon a shaft, working longitudinally in the cylinder. A fresh quantity of oil is then added, if requisite; and the mixture then passes between two sets of cast-iron grinders, by which it is reduced to a very fine and homogeneous paste;— this paste is received in a vessel containing water, and is after wards put into casks for sale. Thus, when the white lead is to be ground up with oil by means of suitably-arranged apparatus, similar to that which we have seen at work, it need not be reduced to very fine powder and sifted; so that one of the most unhealthy of the operations is almost wholly abandoned, and replaced by another, which appears to be perfectly innocuous. It would therefore be very desirable that all the white lead, which, before it is used, must be reduced to paste with oil, should undergo that operation in the course of manufacture; and not in other workshops, where the workmen are exposed to saturnine diseases if suitable precaution be not observed.
It appears certain, from what was observed by one of us in a white lead manufactory at Birmingham, and according to the in formation which we have received from M. le Play, that the English manufactories sell the greater part of their products in the form of paste, which contains from 8 to 9 per cent. of oil. It would be very desirable to follow out this plan in France.
In most of the white lead manufactories great precautions are taken to preserve the health of the workmen. For instance, they are made, on leaving off work, to wash their hands, arms, and faces. For this purpose, there is a plentiful supply of water and soap, potters' earth, and, sometimes, vessels of water holding sulphuret of potassium in solution. In one of the manufactories in Paris sulphur baths are provided, in connection with the boiler of the engine. As regards the insalubrious portions of the work, the workmen are employed upon them alternately, and very rarely several successive days. A room is provided in some establishments, in which the workmen, on leaving off work, deposit their working dress; and, in almost all, the services of a medical man are provided at the expense of the principal. The workshops are in general spacious and airy, more especially those in which the white lead is ground and sifted. The walls and shafts of the machinery become covered with white lead, even when the grind ing apparatus is enclosed; which shews that the pulverizing process must still prove injurious.
From personal observation, and also from information which we have obtained, we are enabled to assert that the general condition of white lead manufactories is not at present so injurious to health as one might be led to imagine from the statistical accounts collected during the last ten years from the hospitals of Paris. There is besides very great difference, as regards salubrity, in the different manufactories which we visited. There was not a single one in which the old processes of manufacture had not undergone some improvement, and in some (we may cite in particular those of M. M. Lefebvre and Co., at Moulins-les-Lille, and of M. Besancon, of Ivry, near Paris) the improvements are very considerable and important. Even in these latter, however, further improvement would be very desirable.
For example, the operations of picking and scouring, and also the pulverization of the dry scales of white lead, have not been rendered perfectly innocuous; for this purpose it would only appear to be necessary to adopt the methods employed in England, and above described.
The manipulation in the process of potting, which, without being absolutely injurious to health, is not without inconvenience, besides causing useless expense, might be dispensed with, if purchasers could be dissuaded from attaching importance to the conical form of the blocks, which in reality it does not possess. If the whole of the white lead which is required to be ground up with oil could be sold in commerce in the form of paste, the in conveniences of reducing the cakes to powder, and packing the powdered white lead in casks, would be considerably lessened, as well as the causes of the maladies which are contracted in grind ing and preparing colors. The carrying of these ameliorations into practical effect does not appear to be attended with any difficulty; but their introduction into manufactories may be prevented, even against the will of the manufacturers themselves, by the prejudices of purchasers, who are wedded to old habits.
In conclusion, the following points seem to be established,— 1st. That the maladies to which the workmen in white lead manufactories are liable may be generally prevented by the substitution of mechanical processes for the manual operations, wherein the workmen are obliged to handle the white lead, as in the following instances: — By the employment of water in the separation of the scales from the residue of lead, and the pulverization and sifting of the scales of white lead. By the substitution of moulding in the form of prisms or bricks, in potting the white lead ground with water. By grinding with oil, by suitable apparatus, during the process of manufacture, such portions of white lead as require to be submitted to that operation before being employed. By enclosing in chambers separated from the workshops all the mechanism necessary for the pulverization and sifting of the white lead, when those operations are indispensably necessary. The dust might be prevented from passing through the openings necessary for the introduction of the materials, and for the working of the shafts of the machinery, by means of currents of air directed towards the interior of the chambers, which must be for that purpose surmounted by a pipe in the form of a chimney, rising above the roof; and also by causing the shafts to work in elastic bearings, or in stuffing-boxes kept constantly lubricated. Lastly, these precautions might be completed by a perfect ventilation of the workshops and hygienic precautions which may be readily observed by the workmen. 2nd. That although many ameliorations favorable to health, recently introduced into most of our white lead manufactories, have consider ably reduced the amount of sickness, there is yet much to be desired, especially as regards the separation of the scales of white lead from the metal, pulverization, and sifting, which precede the grinding with water.
As the commission with which we were charged by the Academy was simply to examine in what respects the white lead manufacture affected the health of the workman,—the casualties therefore resulting from the employment of this substance in the various arts, and the means of preventing them, although of great importance, has formed no part of our enquiry.
With respect to the manufacture itself, your commissioners are of opinion that very important improvements have been effected in relation to the health of the workmen, and that this will cease to be an unhealthy occupation, when it shall be carried on by the improved methods and with the precautions pointed out in this report.
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