The danger of bromine poisoning (especially of the chronic form) is present in its manufacture and use, but there is no positive evidence of the appearance of the bromine rash among the workers. On the other hand, instances are recorded of poisoning by methyl bromide, and the injurious effect of bromide of iodine has been referred to. _Methyl iodide and methyl bromide._—Methyl iodide (CH₃I), a volatile fluid, is obtained by distillation of wood spirit with amorphous phosphorus and iodine; it is used in the production of methylated tar colours and for the production of various methylene compounds. Grandhomme describes, in the paper already referred to, six cases, some very severe, of poisoning by the vapour of methyl iodide among workers engaged in the preparation of antipyrin, which is obtained by the action of aceto-acetic ether on phenyl hydrazine, treatment of the pyrazolone so obtained with methyl iodide, and decomposition of the product with caustic soda. A case of methyl iodide poisoning is described in a factory operative, who showed symptoms similar to those described for methyl bromide except that the psychical disturbance was more marked.[16] Three cases of methyl bromide (CH₃Br) poisoning are described in persons preparing the compound.[17] One of these terminated fatally. There is some doubt as to whether these cases were really methyl bromide poisoning. But later cases of methyl bromide poisoning are known, and hence the dangerous nature of this chemical compound is undoubted. Thus the Report of the Union of Chemical Industry for 1904 gives the following instance: Two workers who had to deal with an ethereal solution of methyl bromide became ill with symptoms of alcoholic intoxication. One suffered for a long time from nervous excitability, attacks of giddiness, and drowsiness. Other cases of poisoning from methyl bromide vapour are recorded with severe nervous symptoms and even collapse. _Fluorine compounds._—_Hydrogen fluoride_ (HFl) commercially is a watery solution, which is prepared by decomposition of powdered fluorspar by sulphuric acid in cast-iron vessels with lead hoods. The escaping fumes are collected in leaden condensers surrounded with water; sometimes to get a very pure product it is redistilled in platinum vessels. Hydrogen fluoride is used in the preparation of the fluorides of antimony, of which antimony fluoride ammonium sulphate (SbFl₃(NH₄)₂SO₄) has wide use in dyeing as a substitute for tartar emetic. It is produced by dissolving oxide of antimony in hydrofluoric acid with addition of ammonium sulphate and subsequent concentration and crystallisation. Hydrofluoric acid is used for etching glass (see also Glass Industry). In brewing, an unpurified silico-fluoric acid mixed with silicic acid, clay, oxide of iron, and oxide of zinc called Salufer is used as a disinfectant and preservative.