Sulphur Coppered

Thiovanadates ana Oxythiovanadates.—A series of crystalline salts is known which resemble the ortho- and pyro-vanadates in composition, except that the oxygen is either wholly or partially replaced by sulphur. Copper orthothiovanadate, Cu3(VS4)2, occurs naturally as sulvanite (see p. 11). The following tliio- and oxythio-compounds have been prepared.3... 

These are largely compounds of sulphur, copper and mercury. Elemental sulphur is probably the oldest effective fungicide known and was recommended as early as the beginning of the nineteenth century to control mildew on fruit trees. The use of Bordeaux mixture on vines has already been mentioned. Other (simple) copper salts (e.g. copper sulphate, cuprous oxide) have also been used as fungicides. Problems with phytotoxicity have led to their replacement by the more effective modern fungicides. 

The earth s crust is a huge mixture of many different compounds. It also contains elements such as sulphur, copper, silver, platinum and gold. These occur uncombined or native because they are imreactive. If you could dig up the earth s crust and break down all the compounds, you would find it is almost half oxygen Its composition is ... 

Beryllium is added to copper to produce an alloy with greatly increased wear resistance it is used for current-carrying springs and non-sparking safety tools. It is also used as a neutron moderator and reflector in nuclear reactors. Much magnesium is used to prepare light nieial allo>s. other uses include the extraction of titanium (p. 370) and in the removal of oxygen and sulphur from steels calcium finds a similar use. 

Crude lead contains traces of a number of metals. The desilvering of lead is considered later under silver (Chapter 14). Other metallic impurities are removed by remelting under controlled conditions when arsenic and antimony form a scum of lead(II) arsenate and antimonate on the surface while copper forms an infusible alloy which also takes up any sulphur, and also appears on the surface. The removal of bismuth, a valuable by-product, from lead is accomplished by making the crude lead the anode in an electrolytic bath consisting of a solution of lead in fluorosilicic acid. Gelatin is added so that a smooth coherent deposit of lead is obtained on the pure lead cathode when the current is passed. The impurities here (i.e. all other metals) form a sludge in the electrolytic bath and are not deposited on the cathode. 

Reduction products vary depending on the reducing agent, for example dinitrogen oxide is obtained with sulphurous acid, nitrogen is obtained when the gas is passed over heated metals (e.g. copper and iron) and ammonia is produced when the gas reacts with aqueous chromiumfll) salts. 

By their oxidising action heating with copper and concen trated sulphuric acid yields brown fumes of nitrogen dioxide. 

It can be prepared by the reduction of hot concentrated sulphuric acid by a metal. Copper is used since it does not also liberate hydrogen from the acid ... 

The iodine is then liberated by heating the copper(I) iodide with sulphuric acid and iron(III) oxide ... 

Sulphur dichloride oxide (thionyl chloride) on the hydrated chloride can also be used to produce the anhydrous chloride in certain cases, for example copper(II) chloride and chromium(III) chloride ... 

Cobalt compounds have been in use for centuries, notably as pigments ( cobalt blue ) in glass and porcelain (a double silicate of cobalt and potassium) the metal itself has been produced on an industrial scale only during the twentieth century. Cobalt is relatively uncommon but widely distributed it occurs biologically in vitamin B12 (a complex of cobalt(III) in which the cobalt is bonded octahedrally to nitrogen atoms and the carbon atom of a CN group). In its ores, it is usually in combination with sulphur or arsenic, and other metals, notably copper and silver, are often present. Extraction is carried out by a process essentially similar to that used for iron, but is complicate because of the need to remove arsenic and other metals. 

By the reduction of copper(II) chloride or a mixed solution of copper(II) sulphate and common salt by sulphur dioxide. 

To prepare pure acetic acid (glacial acetic acid), the crude aqueous product is converted into the sodium salt, the latter dehydrated by fusionf and then heated with concentrated sulphuric acid anhydrous acetic acid, b.p. 118°, distils over. Only the preparation of aqueous acetic acid and of crystalline copper acetate is described below. 

Required Sulphuric acid, 3-3 ml. sodium dichromate, 3-5 g. ethanol, 1-5 ml. copper carbonate, 1 5 g. 

Cuprous bromide. The solid salt may be prepared by dissolving 150 g. of copper sulphate crystals and 87 5 g. of sodium bromide dihydrate in 500 ml. of warm water, and then adding 38 g. of powdered sodium sulphite over a period of 5-10 minutes to the stirred solution. If the blue colour is not completely discharged, a little more sodium sulphite should be added. The mixture is then cooled, the precipitate is collected in a Buchner funnel, washed twice with water containing a little dissolved sulphurous acid, pressed with a glass stopper to remove most of the liquid, and then dried in an evaporating dish or in an air oven at 100 120°. The yield is about 80 g. 

A solution of cuprous bromide may be prepared either by dissolving the solid in hot constant boiling point hydrobromic acid or by refluxing a mixture of 63 g. of crystallised copper sulphate, 20 g. of copper turnings, 154 g. of sodium bromide dihydrate, 30 g. (16-3 ml.) of concentrated sulphuric acid and 1 litre of water for 3-4 hours. If the colour of the solution has not become yellowish after this period of heating, a few grams of sodium sulphite should be added to complete the reduction. 

Preparation of Fehling s solution. Solution No. 1. Dissolve 34-64 g. of A.R. copper sulphate crystals in water containing a few drops of dilute sulphuric acid, and dilute the solution to 500 ml. 

In a 1 5 or 2-Utre rovmd-bottomed flask, prepare cuprous chloride from 105 g. of crystallised copper sulphate as detailed in Section 11,50,1. Either wash the precipitate once by decantation or filter it at the pump and wash it with water containing a httle sulphurous acid dissolve it in 170 ml. of concentrated hydrochloric acid. Stopper the flask loosely (to prevent oxidation) and cool it in an ice - salt mixture whilst the diazo-tisation is being carried out. 

Warm the copper sulphate solution to 50-60°, and add dilute sulphuric acid until it is acid to Congo red. Add the sodium bisulphite solution. 

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