_Biological Test._--Put the substance to be tested into a flask with some small pieces of bread, sterilize for half an hour at 120 deg. C. When cold, inoculate with a culture of _Penicillium brevicaule_, and keep at a temperature of 37 deg. C. If arsenic is present, a garlic-like odour is noticed in twenty four hours, due to arseniuretted hydrogen or an organic combination of arsenic. This test is delicate, and will detect 1/1000 of a milligramme, but it is not quantitative. =Other Preparations of Arsenic.=--These are arsenite of potash (Fowler's solution), cacodylate of sodium, and arsenite of copper (Scheele's green), the last frequently used for colouring dresses and wall-papers. Persons using these preparations may suffer from catarrhal symptoms, rashes on the neck, ears, and face, thirst, nausea, pain in stomach, vomiting, headache, perhaps peripheral neuritis and loss of patellar reflex. The cacodylates, although formerly employed in the treatment of phthisis, should be used with the utmost caution. The arsenites give the reactions of arsenious acid. Arsenic is eliminated not only by the kidneys and bowels, but by the skin, and in women by the menses. It may be detected in the sweat, the saliva, the bronchial secretion, and, during lactation, in the milk. The sale of arsenic and its preparations to the public is properly hedged round with restrictions of all kinds. It is included in Part I. of the Poisons and Pharmacy Act (8 Edward VII., c. 55). No arsenic may be sold to a person under age, nor may it be sold unless mixed with soot or indigo in the proportion of 1 ounce of soot or 1/2 ounce of indigo at the least to every pound of arsenic. =Arseniuretted Hydrogen= (arsine, AsH_{3}) is an extremely poisonous gas, and is evolved in various chemical and manufacturing processes. When damp, _Ferro-silicon_ evolves AsH_{3} and PH_{3}, both very lethal gases. _Ferrochrome_ is used in making steel, and it also evolves PH_{3}, and in such extreme dilution as 0.02 per cent. may cause death. XXII.--ANTIMONY AND ITS PREPARATIONS =Tartar Emetic= (tartarized antimony, potassio-tartrate of antimony) occurs as a white powder, or in yellowish-white efflorescent crystals. Vinum antimoniale contains 2 grains to a fluid ounce of the wine. _Symptoms._--Metallic taste, rapidly followed by nausea, incessant vomiting, burning heat and pain in stomach, purging. Dysphagia, sense of constriction in throat, intense thirst, cramps, faintness, profound depression; in fatal cases, giddiness and tetanic spasms. In _chronic poisoning_, nausea, vomiting and purging, weak pulse, loss of appetite, debility, cold sweats, great prostration, progressive emaciation. The symptoms in chronic poisoning may simulate gastritis or enteritis. Externally applied, it produces an eruption not unlike that of smallpox.