A mirror is a smooth surface capable of regularly reflecting a great proportion of the rays of light that fall upon it. The mirrors used by the ancients, and more especially by the Etruscans, were made of thin polished bronze, either set in a case or fitted with a handle. Small metal mirrors were also used by the Greeks and Romans, and specimens brought by the latter have been found in Cornwall. In England during the middle ages the gentlewomen carried small circular polished metal mirrors attached to their girdles. These were sometimes also fitted into cases with a lid, the material of which was of gold, silver, or ivory, richly designed and ornamented. The making of glass mirrors, which had their backs silvered with an amalgam of mercury and tin, was early practised by the Venetians, and by strict prohibitive statutes they were long able to keep their workmen in Venice and enjoy a monopoly of the trade. The manufacture of mirrors of this kind was first introduced into England early in the 17th century.
The older method of silverizing mirrors by the amalgam of mercury and tin occupied usually a period of weeks, and it has been generally given up. In 1835 Liebig observed that by heating aldehyde in a glass vessel along with an ammoniacal solution of silver nitrate, a coating of brilliant metallic silver was left upon the glass. This has now been made use of in mirror-making by what are known as the hot and cold processes. In the hot process the glass is first sensitised with a solution of tin, which is then rinsed off and the plate laid upon a flat, double-bottomed metal table heated by steam to about 100 degrees Fahrenheit. In this position a solution of silver nitrate, ammonia, and tartaric acid in distilled water is poured over it; and if the temperature is kept uniform a thick deposit of silver will be formed in about half an hour. When the silver layer is carefully wiped this process is repeated.
In the cold process a solution of silver nitrate, ammonium nitrate, and caustic soda dissolved in water, is mixed with a solution of loaf-sugar, vinegar, and water. This is poured quickly and evenly over the glass plate, and the silver is precipitated in a few minutes, after which it is washed and the process repeated. The silvering is then protected by a coating of shellac or copal varnish. More recently a solution of bichloride of platinum is applied to the surface of the glass and precipitated with oil of lavender in the manufacture of the cheapest mirrors.
Mirrors may be plane or spherical, and in the latter case they may be either convex or concave. The optical principles involved in reflection from mirrors are simple.
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Securite is an explosive compound of ammonium nitrate and oxalate, with nitro- or di-nitro-benzene adapted for use in fiery mines as when exploded it is not liable to ignite fire-damp.
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Ammonium Chloride (Sal Ammoniac) is a fibrous mass prepared by neutralising ammonia with hydrochloric acid. It is used in medicine, dyeing and soldering. It has the formulae NH4Cl.
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Minders Spirit is a solution of ammonium acetate, formerly used in medicine to promote sweating in feverish attacks and as a diuretic.
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Nitrogen mustard, in its pure form, occurs as a dark liquid with a faint fishy odour. It is fairly volatile and decomposes slowly on standing, forming the polymeric quaternary ammonium salt. It is very slightly soluble in water. Nitrogen mustard hydrochloride, which is the form produced commercially for sale, is composed of large white, hygroscopic crystals that are soluble in water and methanol. When heated to decomposition, nitrogen mustard emits very toxic fumes of hydrochloric acid and other chlorinated compounds as well as nitrogen oxides (NOx). As formulated for injection,
nitrogen mustard hydrochloride contains 100% +/- 10% active ingredient. Currently, the only known commercial use of nitrogen mustard is as a chemical intermediate in the production of its hydrochloride. Nitrogen mustard hydrochloride is used as an anti-neoplastic agent, either alone or in combination with other chemo-therapeutic agents, to treat neoplastic diseases, including Hodgkin' s disease, leukaemia, generalised lymphosarcoma, mycosis fungoides, and bronchogenic carcinoma. Also, it is used to control pleural, peritoneal, and pericardial effusions caused by metastatic tumours. Clinical investigations have been performed in the past to evaluate its usefulness in treatment of rheumatoid arthritis and a variety of other non-malignant diseases. Research has also been conducted to investigate its use as a chemosterilant and as a cross-linking agent for the manufacture of ion-exchange fibres. Formerly, the pure form of nitrogen mustard was produced for use as a vesicant in chemical warfare.
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Smelling Salts are a preparation of ammonium carbonate with a sweet-scented oil, used in cases of faintness and also formerly to relieve nasal catarrh.
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Amatol (an abbreviation formed from the words 'ammonium' and 'toluene') is a high explosive compound composed of a mixture of ammonium nitrate and trinitrotoluene (TNT).
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Amide Powder is an explosive formerly used as a firearm propellant consisting of ammonium nitrate, potassium nitrate and charcoal. It was also used in German artillery during the Great War.
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Ammonpulver is an explosive formerly used as a firearm propellant by Austria and Germany comprising of ammonium nitrate and charcoal.
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Bellite is a Swedish explosive invented by Carl Lamm in 1885. Bellite resembles sulphur, and smells like pitch and is made up in capsules which look like thick candles and are covered with glazed paper. It is composed of about four parts of ammonium nitrite and one part of a mixture of binitric and trinitro-benzine with potassium nitrate.
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