Ammoniacal cuprous chloride solution

Reaction.—a too c.c. flask to a short upright condenser (see Fig. 86) and to the upper end of the condensei attach a vertical delivery tube, dipping into an ammoniacal cuprous chloride solution. Pour 2—3 c.c. of ethylene bromide into the flask with 4 times its volume of strong methyl alcoholic potash, which is prepared by boiling methyl alcohol with excess of caustic potash on the water-bath with upright condenser. On gently heating, a rapid evolution of acetylene occurs and the characteristic brown copper compound (C2H,Cu,HjO) is precipitated from the cuprous chloride solution. 

The bulk of the carbon dioxide is absorbed by means of water, but if the hydrogen is required for aeronautical purposes, the gas is finally passed through either a caustic soda solution or over lime. Traces of carbon monoxide are removed by passing the gas under pressure through ammoniacal cuprous chloride solution. As a result of these final purifications a gas is obtained of approximately the following composition —... 

The unidentified peak in the chromatogram (Figure 3) gives a negative test for an acetylenic hydrogen (ammoniacal cuprous chloride solution) and does not disappear after the sample is subjected to free radical catalysis for several hours. Thus, the open chain acetylenic isomers of benzene, hexa-l,3-diene-5-yne, 1,4-hexadiyne, 1,5-hexadiyne, and 1,5-hexadien-3-yne do not appear to account for this peak. The possibility of valence isomers of benzene such as bicyclo (2.2.0) hexa-2, 5-diene,... 

B) Cu(NH3)2C1. Place a gram or two of cuprous chloride in each of two dry test tubes. Fill the tubes completely with ammonia water (1 part concentrated ammonia to 2 of distilled water) and immediately close with rubber stoppers. Shake until all the solid is dissolved and note the color of the solution. Then empty out about two-thirds of the contents of one of the tubes and shake the remainder of the solution with the air in the tube. Compare the color of the solution that has been shaken with air with the color of the solution that has not. Explain the change, writing a balanced equation for the reaction between air and ammoniacal cuprous chloride solution. 

Brodie also found that when ammoniacal cuprous chloride solution is added to alkaline sodium peroxide solution, a yellow solution is formed and oxygen is evolved. When nearly all the peroxide is decomposed the evolution of oxygen stops and the solution becomes blue. Brodie thought the yellow colour was due to the intermediate formation and reduction of a peroxide of copper (probably CugOg) ... 

The removal of the 2 per cent, of carbon monoxide is accomplished in a similar tower, only in this case a solution of ammoniacal solution of cuprous chloride is used instead of water. Given an adequate size of tower and volume of the cuprous chloride solution, the pressure at which the gas is introduced into the tower may be as low as 30 atmospheres (441 lb. per sq inch) however, where the gas is to be used for making syndietic ammonia it is usual to compress it to 200 atmospheres (2940 lb. per sq. inch) before passing it tlirough the carbon monoxide absorbing tower. The use of this high pressure is ultimately necessary in the ammonia process and it reduces the size of the tower which has to be employed. 

D) Formation of Metallic Acetylides. Pass acetylene gas for one minute into 5 ml of each of the solutions of ammoniacal silver nitrate and ammoniacal cuprous chloride, prepared according to directions given below. Note the character of the precipitate. Disconnect the flask, and dispose of the material in the flask, according to directions given by the instructor. 

Acetylene and its derivatives of the type R-C=C-H form organo-metallic derivatives with ammoniacal cuprous chloride or with ammoniacal silver nitrate. R-C=C-Ag and R-CsC-Cu. These precipitates although explosive when dry, have been used for quantitative determinations. (Ber. 20, 3081 (1887).) An alcoholic silver nitrate solution precipitates a double salt. 

Metallic Derivatives, (a) Cuprous Acetylide. CujCg. Prepare an ammoniacal solution of cuprous chloride by first adding dilute ammonia to 2-3 ml. of dilute copper sulphate solution until the initial precipitate just redissolves and a clear deep-blue solution is obtained now add an aqueous solution of hydroxylamine hydrochloride drop by drop with shaking until the solution becomes first green and then completely colourless, the cupric salt being thus reduced to the cuprous derivative. 

The only reaction which calls for comment here is the formation of red cuprous acetylide with an ammoniacal solution of cuprous chloride ... 

Cuprous chloride, ammoniacal this solution is used for the same purpose and is made in the same manner as the acid cuprous chloride above, except that the acid solution is treated with ammonia until a faint odor of ammonia is perceptible. Copper wire should be kept with the solution as in the acid reagent. 

Ammoniacal aiptous chloride is made as follows Eoil up copper oxide and metallic copper with cone hydrochloric acid for a short time until the liquid is nearly colourless, and pour the liquid into water. The white cuprous chloride is washed once or twice by decantation and dissolved in a strong solution of ammonium chloride. When required a little ammonia is added sufficient to give a clear blue solution... 

Cuprous acetylide, of which only a very small quantity may be prepared safely at one time, is procured by bubbling acetylene into an ammoniacal solution of cuprous chloride. It precipitates as a brick-red powder. The powder is collected on a small paper filter and washed with water. About 0.1 gram of the material, still moist, is transferred to a small iron crucible—the rest of the cuprous acetylide ought to be destroyed by dissolving in dilute nitric acid—and the crucible is placed on a triangle over a small flame. As soon as the material has dried out, it explodes, with a loud report, causing a dent in the bottom of the crucible. 

The last-named compound is converted into the copper derivative by dissolving it in much alcohol and adding an ammoniacal solution of cuprous chloride. The resulting precipitate is washed with ammonia, then beaten to a pulp and air bubbled through it to remove ammonia it may be recrystallised from chloroform. 

Copper pyrites may be obtained in the laboratory in the wet way by shaking a weakly ammoniacal solution of cuprous chloride with potassium ferric sulphide until the solution no longer contains copper —6... 

A mixture of ethane, ethylene and acetylene can be resolved into its constituents by first passing the gaseous mixture through an ammoniacal solution of cuprous chloride which retains acetylene as a precipitate of cuprous acetylide. 

Its presence may be detected by the formation in an ammoniacal solution of cuprous chloride of a blood red precipitate, which is explosive when diy. It is probable that enlosions which sometimes occur in bxase or copper pipes, through which illuminating gas is conducted, are due to the formation of this compound. 

The reactions of acetylene which have been mentioned are analogous to those of the unsaturated hydrocarbons containing a double bond. Acetylene and other compounds which contain a carbon atom in combination with hydrogen and joined to a second atom in the manner which is represented by a triple bond, that is, those containing the group H —C =, show characteristic properties which serve to distinguish them from other substances. Such compounds are converted into metallic derivatives when they are treated with an ammoniacal solution of cuprous chloride or of silver chloride. If acetylene is passed into a solution of cuprous chloride in ammonia, a red precipitate is formed which has the composition C2CU2. This compound, which is a carbide of copper, is usually called copper acetylide. It explodes, when dry, if it is struck or is heated to 100°-120°. When treated with hydrochloric acid or with a solution of potassium cyanide, acetylene is formed. 

Write equations for reactions which take place when allylene is treated with (a) bromine, (Jb) an ammoniacal solution of cuprous chloride, and (c) hydriodic acid. 

Silver acetylide, Ag2C2, is a white powder formed when acetylene is passed through an ammoniacal solution of silver chloride. It has even stronger explosive properties than cuprous acetylide due to its exceptionally large negative heat of formation —87.15 kcal/mole). Its ignition temperature is 200°C. It is of... 

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