Lewin has described a case in which a worker scattering a mixture of basic slag and ammonium superphosphate suffered from an eczematous ulceration which, on being scratched by the patient, became infected and led to death from general blood poisoning. Lewin regarded the fatal issue as the sequela of the scattering of the manure. Inflammation of the conjunctiva and of the eyelids has been recorded. CHROMIUM COMPOUNDS AND THEIR USES Chrome ironstone, lime, and soda are ground and intimately mixed. They are next roasted in reverberatory furnaces, neutral _sodium chromate_ being formed. This is lixiviated and converted into sodium bichromate (Na₂Cr₂O₇) by treatment with sulphuric acid. Concentration by evaporation follows; the concentrated liquor is crystallised in cast-iron tanks. The crystals are centrifugalised, dried, and packed. _Potassium bichromate_ may be made in the same way, or, as is usually the case, out of sodium bichromate and potassium chloride. The bichromates are used in the preparation and oxidation of chrome colours, but their principal use is in dyeing and calico printing, bleaching palm oil, purifying wood spirit and brandy, in the preparation of ‘Swedish’ matches, in the manufacture of glass, in photography, in dyeing, in tanning, and in oxidation of anthracene to anthraquinone. Lead Chromate and Chrome Colours _Chrome yellow_ is neutral lead chromate (PbCrO₄). It is obtained by precipitating a solution of potassium bichromate with lead acetate or lead nitrate, or by digesting the bichromate solution with lead sulphate, and is used as a paint and in calico and cloth printing. With Paris or Berlin blue it forms a _chrome green_. _Chrome orange_, i.e. basic lead chromate (PbCrO₄Pb(OH)₂) is made by adding milk of lime to lead chromate and boiling. _Chromium_ and _chromic acid salts_ are widely used in dyeing and printing, both as mordants and oxidising agents and as dyes (chrome yellow, chrome orange). In mordanting wool with potassium chromate the wool is boiled in a potassium chromate solution to which acids such as sulphuric, lactic, oxalic, or acetic are added. In dyeing with chrome yellow, for instance, the following is the process. Cotton wool is saturated with nitrate or acetate of lead and dried, passed through lime water, ammonia, or sodium sulphate, and soaked in a warm solution of potassium bichromate. The yellow is converted into the orange colour by subsequent passage through milk of lime. _Chrome tanning._—This method of producing chrome leather, first patented in America, is carried out by either the single or two bath process. In the two bath process the material is first soaked in a saturated solution of bichromate and then treated with an acid solution of thiosulphate (sodium hyposulphite) so as to reduce completely the chromic acid. The process is completed even with the hardest skins in from two to three days.