Use of chrome salts (especially potassium bichromate) in the preparation of the paste causes risk of poisoning in premises where ‘Swedish’ matches are made. Attention has been called to the frequency of chrome ulceration.[4] The paste used consists of 3-6 per cent. chrome salt, so that each match head contains about ½ mg. Wodtke found among eighty-four workers early perforation of the septum in thirteen. Severe eczema also has been noted. It is even alleged that red phosphorus is not entirely free from danger. Such cachexia as has been noted may be referable to the absorption of potassium chlorate. Other Uses of Phosphorus and Compounds of Phosphorus Isolated cases of phosphorus poisoning have been observed in the manufacture of phosphor-bronze. This consists of 90 parts copper, 9 parts tin, and 0·5 to 0·75 phosphorus. _Sulphides of phosphorus_ (P₂S₅, P₄S₃, P₂S₃) are made by melting together red phosphorus and sulphur. They make a satisfactory substitute for the poisonous yellow phosphorus and are considered non-poisonous, but the fact remains that they give off annoying sulphuretted hydrogen gas. _Phosphoretted hydrogen gas_ (PH₃) rarely gives rise to industrial poisoning. It may come off in small amounts in the preparation of acetylene and in the preparation of, and manipulations with, white phosphorus. It is stated that in acetylene made of American calcium carbide 0·04 per cent. of phosphoretted hydrogen is present, and in acetylene from Swedish calcium carbide 0·02 per cent.; Lunge and Cederkreutz found an acetylene containing 0·06 per cent. These amounts might cause poisoning if the gas were diffused in confined spaces. Poisoning, in part attributable to phosphoretted hydrogen gas, is brought about through ferro-silicon (see under Ferro-silicon). Superphosphate and Artificial Manure _Superphosphate_, an artificial manure, is prepared from various raw materials having a high proportion of insoluble basic calcium phosphate (tricalcium phosphate), which by treatment with sulphuric acid are converted into the soluble acid calcium phosphate (monocalcium phosphate) and calcium sulphate. Mineral substances such as phosphorites, coprolites, guano, bone ash, &c., serve as the starting-point. Chamber acid, or sometimes the waste acid from the preparation of nitro-benzene or purification of petroleum, are used in the conversion. The raw materials are ground in closed-in apparatus, under negative pressure, and mixed with the sulphuric acid in wooden lead-lined boxes or walled receptacles. The product is then stored until the completion of the reaction in ‘dens,’ dried, and pulverised in disintegrators. In the manufacture of bone meal extraction of the fat from the bones with benzine precedes treatment with acid.