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LIQUID CHLORINE.

[Par. 5, act of 1913. 15 per cent ad valorem.]

SUMMARY.

Description. Chlorine is one of the chemical elements which at ordinary atmospheric conditions is a gas. It has a greenish yellow color. When subjected to pressure and refrigeration the gas liquefies, forming the liquid chlorine of commerce, which is shipped in steel cylinders. Chlorine is used in the preparation of many chemical compounds, the more important ones are bleaching powder, carbon tetrachloride, monochlorbenzol, chloroform, monochloracetic acid, tin chlorides, sulphur chlorides, and phosgene. Liquid chlorine is rapidly taking the place of bleaching powder in the purification of public water supplies.

Domestic production.-The 1914 census shows about 6,000 short tons, valued at $472,836, as being produced in the United States. Calculating from the quantity of electrolytic caustic soda produced in 1917, there was produced simultaneously 112,400 short tons of chlorine gas. Only part of this quantity was marketed, the remainder being used in the plants where produced.

Chlorine is produced in this country exclusively by the electrolytic process. In Europe it is also produced by the Weldon and Deacon

processes.

Chlorine is produced as a joint product with caustic soda. Since electricity is used in the manufacture it follows that large quantities should be made at Niagara Falls. This industry, however, is not as dependent on cheap water power as the other electrochemical industries, and there are several plants located in different parts of the country which produce chlorine.

There is no direct competition from foreign sources in liquid chlorine, only chlorine products such as bleaching powder being imported.

The installation of an electrolytic chlorine plant involves a considerable initial outlay of capital for buildings, power equipment, and electrolytic cells.

Price.-Liquid chlorine sells at about 15 cents per pound. It has only been quoted on the open market since about July, 1916.

Tariff history.-Chlorine or liquid chlorine has not been mentioned by name in any of the tariff acts.

GENERAL INFORMATION.

Description.-Chlorine is one of the elements which at ordinary temperatures and pressures is a greenish-yellow gas. It is never found free in nature, but occurs in the combined form chiefly as the chloride of sodium, potassium, calcium, and magnesium. Of these compounds, the chloride of sodium (salt) is the source of all the chlorine produced in the United States.

Chlorine, even when greatly diluted with air, has a characteristic irritating odor. It can not be breathed to any extent, as it readily attacks the membranes and is very suffocating. When inhaled in small quantities it produces colds and larger quantities cause vomiting and the spitting of blood. The gas is incombustible in air, but burns in an atmosphere of hydrogen with the formation of hydrochloric acid. Chlorine can be liquefied by cooling the gas to minus 34° C. or by subjecting it to a pressure of about 6 atmospheres. It is this property and the fact that dry chlorine does not attack iron or steel that has made practicable the shipment of chlorine as a liquid in iron and steel cylinders.

Chlorine is a very active chemical agent and combines with many substances at ordinary temperatures. The presence of water causes chlorine to act on many substances that in the dry state would be unaffected. Dry chlorine by itself or in the presence of sulphuric acid has no action on cast iron, wrought iron, steel, phosphor bronze, brass, copper, zinc, or lead.

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Raw materials.Chlorine is produced in this country exclusively by the electrolysis of solutions of sodium chloride (salt). The salt for this purpose should be pure, or must be purified before being electrolyzed. The salt particularly should contain no sulphates or barium salts. With very few exceptions, the salt produced in this country is admirably suited for the manufacture of chlorine by the electrolytic method.

Process of manufacture. The production of chlorine in the United States consists in passing a direct electric current through a solution of salt in a suitable apparatus, which is known as an electrolytic cell. Since the details of the manufacture vary with the type of electrolytic cell used, only the essential steps in the process will be described.

Common salt is dissolved in water to form a saturated solution which is purified by treatment with soda ash, thus removing any calcium, magnesium, iron, or barium salts that may be present. The solution is then allowed to settle or is filtered to remove the precipitated impurities. The clear solution of salt is then fed to the electrolytic cells either as a neutral acid or alkaline solution according to individual practice. The salt solution as it passes through the cell is subjected to the action of the electric current which decomposes the salt into chlorine and sodium. The chlorine gas is withdrawn from the cells by means of a vacuum on the chlorine compartment of the cell.

For the production of liquid chlorine the gas is now thoroughly dried, usually by the means of concentrated sulphuric acid. It is then compressed by means of a special type of compressor and then subjected to refrigeration which causes it to liquefy. The resulting liquid chlorine is stored and shipped in steel cylinders which hold about 150 pounds of chlorine. These cylinders are tested to withstand about 600 pounds pressure. The chlorine by liquefaction is reduced in volume in about the ratio of 400 to 1.

It is advantageous to have a source of cheap electrical power, such as water power for the manufacture of chlorine. This factor, however, does not appear to be of as vital importance in this industry as in the other electrochemical industries. There are several electro

lytic chlorine plants which produce their electric current for electrolysis by steam installations.

The manufacture of electrolytic chlorine requires a relatively small amount of labor, as the process is continuous and to a large extent automatic.

The principal types of electrolytic chlorine cells used in the United States are the Townsend, Castner-Kellner, Dow, Gibbs, Nelson, AllenMoore, Wheeler, and the Billiter-Siemens.

In addition to the electrolytic method, chlorine is produced in Europe by two other processes, the Weldon and Deacon. The former consists in producing chlorine by the oxidation of hydrochloric acid by the means of manganese dioxide (pyrolusite). The latter process produces chlorine by passing a mixture of hydrochloric acid gas and air over copper salts at a temperature of about 460° C. Both of these processes are more complicated than the electrolytic one.

Important uses.-Chlorine is used in the manufacture of the following products: Bleaching powder, carbon tetrachloride, chloroform, sulphur chlorides, chloral hydrate, monochloracetic acid, phosphorus chlorides, phosgene, tin chlorides, iron chloride, aluminum chloride, acetylene tetrachloride, ethylene chloride, methane chlorides, bromine. Chlorine is used in the chlorination of many organic compounds, such as benzol, toloul, napthalene, and anthracene.

It is used directly or in the form of bleaching powder for the bleaching of cotton and linen goods.

Liquid chlorine is practically supplanting bleaching powder for the purification of water supplies, especially in the larger cities.

Chlorine is used to some extent in the recovery of gold and silver. This use at one time was very promising but has not met with the success that was expected and therefore this use of chlorine is decreasing.

It is used as an oxidizing agent in the manufacture of arsenic acid in the preparation of lead arsenate.

History of the industry.-Chlorine has been known since 1774 when it was first prepared by Scheele. The industrial application of chlorine was developed during the years following 1868. During this time the Weldon and Deacon processes were put into successful operation on an industrial scale. Both of these processes have never been introduced into this country. In 1897 the electrolytic chlorine industry was established in the United States for the manufacture of bleaching powder.

The development of the liquefaction of chlorine began in Europe in about 1890 and since that time has gained considerable importance. The liquefying of chlorine and the development of the uses for liquid chlorine in this country have been within recent years. Since the introduction of liquid chlorine in the United States the industry has progressed rapidly, owing to the increased demands for liquid chlorine as a bleaching agent and for the purification of public water supplies.

The chief disadvantage of liquid chlorine is the initial cost of the cylinders and the fact that the cylinders must be returned to the manufacturer for refilling. This latter fact makes it doubtful whether liquid chlorine will completely replace bleaching powder as a means of exporting chlorine.

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1 The Geological Survey reported the production of 126,570 short tons of caustic soda as being produced electrolytically. Simultaneously there would have been produced about 112,400 short tons of chlorine. This amount was not all marketed, as some was consumed in the plants where produced.

Liquid chlorine-Prices, wholesale (cents per pound), spot New York.

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CAFFEINE AND CAFFEINE COMPOUNDS.

[Par. 13, act of 1913.]

SUMMARY.

The manufacture of the alkaloid, caffeine, in the United States is a relatively small industry and is restricted to a few firms. Prior to the war it supplied approximately two-thirds of the domestic consumption, and has an output of about 150,000 pounds, worth in the neighborhood of $500,000. Its principal competitor, the German chemical industry, was cut off from the American market in 1915, and imports immediately fell from 54,000 pounds in 1915 to an average of less than 3,000 pounds for the period 1916-1920. The domestic production had increased in 1919 to 241,615 pounds, valued at $1,673,682. The price of the alkaloid, which was about $3.25 per pound in 1914, has practically doubled since that time. During the scarcity in 1916 it reached a maximum of $17 per pound.

Although a number of familiar plant products contain caffeine, the raw material best suited for its commercial manufacture has proved to be the dust, sweepings, and waste obtained from the tea industry. A very small quantity of caffeine is obtained from the dust and crustations recovered from the flues of coffee-roasting plants, while in Germany the product was prepared prior to the war by extraction of the whole coffee beans. The coffee so extracted was sold as "decaffeinated" coffee. The process was also put into operation in this country, and some caffeine is reported to have been produced in this way. Caffeine has also been prepared synthetically from uric acid. Caffeine and its compounds are used in medicine, but the predominant use is in the manufacture of soft drinks of the Coca Cola type.

The Japanese chemical industry is now attempting to secure Germany's former position as a dominating factor in the caffeine trade. Japan possesses several competitive advantages, the most important of which, perhaps, is her close proximity to an abundant source of the raw material. Tea waste, which contains only about 2 per cent of caffeine, is a very bulky material, and the American manufacturers have found its transportation expensive as well as difficult to secure.

The tariff problem of chief interest is the relation between the rates of duty on the raw material and the finished product. Since 1913 the former has been dutiable at 1 cent per pound and the rate on caffeine has been $1 per pound. Since about 50 pounds of tea waste are required to produce 1 pound of caffeine, the duty on the raw material amounts to 50 cents per pound of caffeine contained. This duty, together with the large difference in ocean-freight rates, favors the importation of the prepared alkaloid rather than its raw material.

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