Alkali manufacture 3966807 222041457 2008-06-27T08:08:09Z Biscuittin 3955768 added link :''This is a historical article. For current information see [[Sodium_hydroxide#Manufacture]] and [[Chloralkali process]].'' '''Alkali manufacture''' is the process by which an [[alkali]] is made. Typical alkalis, produced commercially, include [[sodium hydroxide]], [[sodium carbonate]], [[potassium hydroxide]] and [[potassium carbonate]]. A number of processes have been proposed for the manufacture of alakali from various metals, the most common being the Leblanc and ammonia-soda processes. <!-- but since in the Leblanc process the manufacture of sodium sulfate necessarily precedes that of the carbonate, we include this as well as the manufacture of hydrochloric acid which is inseparable from it. We also treat of the utilization of hydrochloric acid for the manufacture of chlorine and its derivatives, which are usually comprised within the meaning of the term "alkali manufacture." A great many processes have been proposed for the manufacture of alkali from various materials. --> == The Leblanc Process == :''Main article: [[Leblanc process]] The Leblanc process, which was invented by [[Nicolas Leblanc]] around [[1790]], begins with the decomposition of [[sodium chloride]] by [[sulfuric acid]], by which sodium sulfate and [[hydrochloric acid]] are produced. The sodium sulfate is afterwards fired with [[calcium carbonate]] and [[coal]]. Sodium carbonate can be extracted from this mixture by washing the mixture with water. Until the rise of the ammonia-soda process, which has better economics, the Leblanc process was used extensively giving the [[United Kingdom]] a lead in alkali production. It should be noted that the UK's production outstripped that of all other producers combined.{{Fact|date=February 2007}}, a trend still evident in modern times.{{Fact|date=February 2007}} <!-- "Modern times" in this context means 1911 (see discussion page) --> Most of the British alkali works are situated in [[Lancashire|South Lancashire]] and the adjoining part of [[Cheshire]], near the mouth of the [[Tyne]] and in the West of [[Scotland]]. <!-- The production of alkali in [[Great Britain]], soon after the introduction of the Leblanc process, became the most extensive in the world, and outstripped that of all other countries put together. With the rise of the ammonia-soda process, for which the economic conditions are nearly as favorable in other countries, the predominance of Great Britain in that domain has become less, but even now that country produces more alkali than any other single country. --> == The Ammonia-Soda Process == :''Main article: [[Solvay process]]'' Despite improvements made to the [[Leblanc Process]], economics determines that it cannot compete effectively against the [[ammonia-soda process]] which is now more common.{{Fact|date=February 2007}} There are a number of reasons for this: * The sodium used in the process is practically free. * The fuel requirement is halved. * Efficiency improvements have reduced 'waste' in the process to a minimum. <!--In spite of the great improvements effected during recent times the [[Leblanc process]] cannot economically compete with the [[Ammonia-Soda Process]], principally for two reasons. --> <!-- The sodium in the latter costs next to nothing, being obtained from natural or artificial brine in which the sodium chloride possesses an extremely slight value. The fuel required is less than half the amount used in the Leblanc process. Moreover, the ammonia process has been gradually elaborated into a very complicated but perfectly regularly working scheme, in which the cost of labor and the loss of ammonia are reduced to a minimum. --> The only way in which the Leblanc process could still hold its own was by being turned in the direction of making [[caustic soda]], to which it lends itself more easily than the ammonia-soda process; but the latter has invaded even this field. One advantage, however, still remained to the Leblanc process. All endeavours to obtain either [[hydrochloric acid]] or free chlorine in the [[ammonia-soda process]] have proved commercial failures; all the chlorine of the sodium chloride being ultimately lost in the shape of worthless calcium chloride. The Leblanc process thus remained the sole purveyor of chlorine in its active forms, and in this way the fact is accounted for that, at least in Great Britain, the Leblanc process still furnishes nearly half of all the alkali made, though in other countries its proportional share is much less. The profit made upon the chlorine produced has to make up for the loss on the alkali. The ammonia-soda process was first patented in [[1838]] by H. G. Dyar and J. Hemming, who carried it out on an experimental scale in [[Whitechapel]]. Many attempts were soon after made in the same direction, both in England and on the continent of Europe, the most remarkable of which was the ingenious combination of apparatus devised by J. J. T. Schloesing and E. Rolland. But a really economical solution of the problem was first definitely found in [[1872]] by [[Ernest Solvay]], as the result of investigations begun about ten years previously. The greater portion of all the [[Soda ash|soda-ash]] of commerce is now made by Solvay's apparatus, which alone shall be described in this place, although it should be borne in mind that the principles laid down by Dyar and Hemming have been and are still successfully carried out in a number of factories by an entirely different kind of apparatus. ==Other processes== * [[Castner-Kellner process]] * [[Nelson's process]] ==Sources== {{1911}} [[Category:Chemical processes]] [[Category:Industrial processes]]