Concentrated Hydrochloric Acid Monochloride

Iodine monochloride, formed when iodine reacts with the iodate(V) ion in the presence of an excess of concentrated hydrochloric acid. 

Arsenic trichloride (arsenic(III) chloride), AsQ. is the most common and important haUde of arsenic. It may be formed by spontaneous combination of the elements and, in addition, by the following reactions (/) chlorine with arsenic trioxide (2) sulfur monochloride, 82(11, or a mixture of S2CI2 chlorine, with arsenic trioxide and (J) arsenic trioxide with concentrated hydrochloric acid or with a mixture of sulfuric acid and a chloride. 

C) Preparation of 0-(3-Amino-2,4,6-Triiodophenylj-a-Ethylpropionic Acid A solution of 5.0 g of m-amino-o -ethylhydrocinnamic acid in 100 cc of water containing 5 cc of concentrated hydrochloric acid is added over a period of A hour to a stirred solution of 3.2 cc of iodine monochloride in 25 cc of water and 25 cc of concentrated hydrochloric acid... 

The compound is generally made from arsenic trioxide by (i) passing chlorine over it or (ii) treating the trioxide with sulfur monochloride, S2CI2. Alternatively it is prepared from arsenic trioxide by distdlation with either concentrated hydrochloric acid or a mixture of sulfuric acid and a metal chloride. Arsenic trichloride may also be prepared by combination of arsenic and... 

The crude 5-amino-N-methylisophthalamic acid was dissolved in hydrochloric acid (100 ml concentrated acid and 100 ml of water) and this solution was diluted to 1 liter with water. Iodine monochloride (27.4 g of 95% ICI, 0.16 mole) in concentrated hydrochloric acid (30 ml) was added in one portion to the stirred solution maintained at 54°C. The solution was heated on a steam bath. After 2 hours the solution was diluted to 1.5 liters and after 3 hours titration of an aliquot indicated that 50% of the iodine monochloride had been consumed. Precipitation of a solid began after 33/4 hours of reaction (75°C). Intermittent heating and stirring was continued for 4 days, 10 g of 95% iodine monochloride was added during the third day. After 4 days, titration of an aliquot indicated that 96% of the theoretical quantity of iodine monochloride had been consumed. The precipitated solid was filtered off, washed with water and dried at 75°C under reduced pressure. Yield of 5-amino-2,4,6-triiodo-N-... 

A solution of 5.0 g of a-ethyl-p-(aminophenyl)propionic acid in 100 ml of water containing 5 ml of concentrated hydrochloric acid was added over a period of Vi hour to a stirred solution of 3.2 ml of iodine monochloride in 25 ml of water and 25 ml of concentrated hydrochloric acid heated to 60°C. After addition was complete, the heating was continued for Vi hour longer at 60° to 70°C. A black oil separated which gradually solidified. The mixture was then cooled and sodium bisulfite was added to decolorize. Recrystallization of the product from methanol gave about 8 g of a-ethyl-p-(2,4,6-triiodo-3-aminophenyl)-propionic acid, MP 147° to 150°C. The product could be further purified by precipitation of its morpholine salt from ether solution and regeneration of the free amino acid by treatment of a methanol solution of the morpholine salt with sulfur dioxide. The pure amino acid had the MP 155° to 156.5°C (corr). 

In a 3-I. beaker, no g. (0.8 mole) of anthranilic acid (Note 1) is dissolved in 11. of water and 80 cc. of c.f. concentrated hydrochloric acid (sp. gr. 1.19), and the solution is cooled to 20°. In a 2-1. beaker a solution of iodine monochloride in hydrochloric acid is prepared by diluting 140 cc. of c.p. concentrated hydrochloric acid with 500 cc. of cold water, adding just sufficient crushed ice to bring the temperature to 50, and, during about two minutes, stirring in 131 g. (0.8 mole) of iodine monochloride (Org. Syn. 12, 29). 

In very concentrated hydrochloric acid (3-6 mol/L), an iodatometry at four electrons occurs. This is the base of Andrews method. Iodine monochloride is formed. The corresponding half-redox equilibrium is... 

Dissolve a quantity of sample to contain about 0 25 g of ferrous iron in 20 ml of 25 per cent w/v sulphuric acid, add 6 ml of strong iodine monochloride solution and 60 ml of concentrated hydrochloric acid and titrate with 0 05M potassium iodate, using 5 ml of chloroform as indicator. 1 ml 0-05M potassium iodate = 0 01117 g Fe 0 02317 g FeCOa 0 03038 g FeS04. 

The strong iodine monochloride reagent is prepared as follows dissolve 6 44 g of potassium iodate and 10 g of potassium iodide in 75 ml of water add 75 ml of concentrated hydrochloric acid and shake until a clear solution is obtained add 5 ml of chloroform and titrate with 0 05M iodate to the disappearance of the trace of liberated iodine. 

Niobium Pent chloride. Niobium pentachloride can be prepared in a variety of ways but most easily by direct chlorination of niobium metal. The reaction takes place at 300—350°C. Chlorination of a niobium pentoxide—carbon mixture also yields the pentachloride however, generally the latter is contaminated with niobium oxide trichloride. The pentachloride is a lemon-yeUow crystalline soHd that melts to a red-orange Hquid and hydrolyzes readily to hydrochloric acid and niobic acid. It is soluble in concentrated hydrochloric and sulfuric acids, sulfur monochloride, and many organic solvents. 

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