Copper salts, fractionation using

Today the sulphonation route is somewhat uneconomic and largely replaced by newer routes. Processes involving chlorination, such as the Raschig process, are used on a large scale commercially. A vapour phase reaction between benzene and hydrocholoric acid is carried out in the presence of catalysts such as an aluminium hydroxide-copper salt complex. Monochlorobenzene is formed and this is hydrolysed to phenol with water in the presence of catalysts at about 450°C, at the same time regenerating the hydrochloric acid. The phenol formed is extracted with benzene, separated from the latter by fractional distillation and purified by vacuum distillation. In recent years developments in this process have reduced the amount of by-product dichlorobenzene formed and also considerably increased the output rates. 

The distillate should be collected in the 200-ml. round-bottomed flask which is used in the subsequent fractionation. The distillation takes about an hour. The cake of copper salts in the flask is best removed by digestion with concentrated ammonium hydroxide solution. 

The biuret method The bimet method is a colorimetric technique specific for proteins and peptides. Copper salts in alkaline solution form a pruple complex with substances containing two or more peptide bonds. The absorbance produced is proportional to the number of peptide bonds that are reacting and therefore to the number of protein molecules present in the reaction system. Thus, the biuret reaction with proteins is suitable for the determination of total protein by spectrophotometry (at 540-560 nm). The method is used extensively in clinical laboratories, particularly in automated analyzers in which protein concentration can be measured down to 0.1-0.15gl. The use of bovine or human serum albumin to standardize the biuret method is well established. ITigh-purity albumin contains only amino acids its nitrogen content is a constant fraction... 

H. M. Dawson and J. McCrae, D. P. Konowaloff, and W. Gaus also used soln. of various salts of the alkali metals, and of potassium, sodium, cupric, or barium hydroxide in place of water and also copper sulphate, copper chloride, zinc sulphate, and cadmium iodide while M. 8. Sherrill and D. E. Russ examined the effect of ammonium chromate. W. Herz and A. Kurzer examined the distribution of ammonia between water and a mixture of amyl alcohol and chloroform. Observations on the distribution of ammonia between water and chloroform were made by T. S. Moore and T. F. Winmill, G. A. Abbott and W. C. Bray, and J. M. Bell. J. H. Hildebrand gave for the molar fraction N X104 of ammonia at 1 atm. press., and 25°, dissolved by ethyl alcohol, 2300 methyl alcohol, 2730 and water, 3300. 

Air contains molecular nitrogen and oxygen. They may be separated by liquefaction and fractional distillation along with inert gases, especially argon. Salt or brine can be used as sources of chlorine and sometimes bromine, sodium hydroxide, and sodium carbonate, whereas metals such as iron, aluminum, copper, or titanium as well as phosphors, potassium, calcium, and fluorine are obtained from mineral ores. Saltpeter was once an important source of nitrogen compounds, but today most ammonia and nitrates are produced synthetically from nitrogen gas in the air. 

The presence of ammonium ions in the alkaline copper increases the blank color, but decreases the blue-violet color produced from protein. This effect occurs at concentrations down to 0.05 M (S41), so that albumin in ammonium sulfate solutions must first be isolated before the quantitative biuret reaction can be applied. When present in higher concentrations, sodium sulfate and most other salts used for fractionating protein solutions intensify the biuret color (R27). However, the absorbance of the blank alkaline copper solutions containing no protein is also affected to the same extent, making it unnecessary to isolate the soluble protein before applying the biuret reaction. 

Mixtures of acetaldehyde and acetic acid may be obtained121 by passing acetylene (2 to 3 volumes) and air (10 volumes) mixed with a large excess of steam over the zinc, copper, nickel, or cadmium salts of vanadic, molybdic, or chromic acids deposited upon a suitable base, such as pumice, at temperatures ranging from 300° to 400° C. For example, yields of 75 to 80 per cent acetaldehyde along with 5 per cent acetic acid have been obtained by using basic zinc vanadate at 380° C. The aldehyde is separated by fractional condensation in a column and the condensed fraction which is poor in aldehyde is utilized to furnish steam for the catalytic treatment of more acetylene. The fractions rich in acetaldehyde serve for the direct recovery of the aldehyde or may be oxidized immediately to acetic acid by passage over a suitable catalyst. In this way, the process may also be applied directly to the preparation of acetic acid from acetylene. 

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