Chlorine rash has been observed in an alkali works where chlorine was not produced electrolytically, and under conditions which suggested that compounds of tar and chlorine were the cause. In this factory for the production of salt cake by the Hargreaves’ process cakes of rock salt were prepared and, for the purpose of drying, conveyed on an endless metal band through a stove. To prevent formation of crusts the band was tarred. The salt blocks are decomposed in the usual way by sulphur dioxide, steam, and oxygen of the air, and the hydrochloric acid vapour led through Deacon towers in which the decomposition of the hydrochloric acid into chlorine and water is effected by metal salts in the manner characteristic of the Deacon process. These salts are introduced in small earthenware trays which periodically have to be removed and renewed; the persons engaged in doing this were those affected. The explanation was probably that the tar sticking to the salt blocks distilled in the saltcake furnaces and formed a compound with the chlorine which condensed on the earthenware trays. When contact with these trays was recognised as the cause, the danger was met by observance of the greatest cleanliness in opening and emptying the Deacon towers.
Leymann[2] is certain that the rash is due to chlorinated products which emanate from the tar used in the construction of the cells. And the affection has been found to be much more prevalent when the contents of the cells are emptied while the contents are still hot than when they are first allowed to get cold.
Lehmann[3] has approached the subject on the experimental side, and is of opinion that probably chlorinated tar derivatives (chlorinated phenols) are the cause of the trouble. Both he and Roth think that the affection is due not to external irritation of the skin, but to absorption of the poisonous substances into the system and their elimination by way of the glands of the skin.
In the section on manganese poisoning detailed reference is made to the form of illness recently described in persons employed in drying the regenerated Weldon mud.
Mercurial poisoning is possible when mercury is used in the production of chlorine electrolytically.
In the manufacture of chlorates and hypochlorite, bleaching fluids, &c., injury to health from chlorine is possible in the same way as has been described above.
OTHER CHLORINE COMPOUNDS. BROMINE, IODINE, AND FLUORINE
Chlorine is used for the production of a number of organic chlorine compounds, and in the manufacture of bromine and iodine, processes which give rise to the possibility of injury to health and poisoning by chlorine; further, several of the substances so prepared are themselves corrosive or irritating or otherwise poisonous. Nevertheless, severe poisoning and injurious effects can be almost entirely avoided by adoption of suitable precautions. In the factory to which Leymann’s figures refer, where daily several thousand kilos of chlorine and organic chlorine compounds are prepared, a relatively very favourable state of health of the persons employed was noted. At all events the preparation of chlorine by the electrolytic process takes place in closed vessels admirably adapted to avoid any escape of chlorine gas except as the result of breakage of the apparatus or pipes. When this happens, however, the pipes conducting the gas can be immediately disconnected and the chlorine led into other apparatus or into the bleaching powder factory.
As such complete precautionary arrangements are not everywhere to be found, we describe briefly the most important of the industries in question and the poisoning recognised in them.
Chlorides of phosphorus.—By the action of dry chlorine on an excess of heated amorphous phosphorus, trichloride is formed (PCl₃), a liquid having a sharp smell and causing lachrymation, which fumes in the air, and in presence of water decomposes into phosphorous acid and hydrochloric acid. On heating with dry oxidising substances it forms phosphorus oxychloride (see below), which is used for the production of acid chlorides. By continuous treatment with chlorine it becomes converted into phosphorus pentachloride (PCl₅), which also is conveniently prepared by passing chlorine through a solution of phosphorus in carbon bisulphide, the solution being kept cold; it is crystalline, smells strongly, and attacks the eyes and lungs. With excess of water it decomposes into phosphoric acid and hydrochloric acid: with slight addition of water it forms phosphorus oxychloride (POCl₃). On the large scale this is prepared by reduction of phosphate of lime in the presence of chlorine with carbon or carbonic oxide. Phosphorus oxychloride, a colourless liquid, fumes in the air and is decomposed by water into phosphoric acid and hydrochloric acid.