Educator Indian Journal of Chemical Technology Vol. 10. January 2003. pp. 99-112 Sodium carbonate--From natural resources to Leblanc and back Jaime Wisniak Department of Chemical Engineering, Ben-Gurion University of the Negev, Beer-Sheva, Israel 84105 The development of sodium carbonate as a major commodity is intimately attached to the chemical revolution that took place in the eighteenth and nineteenth century. Strong politiclil and economical reasons led to the search of synthetic procedures to replace the natural sources of soda that were available by the seventeenth century. Eventually Nicolas Leblanc developed a synthetic process that used qommoQ salt as raw material. lmplfmentation of Leblanc's procedure led to such serious environmental problems, e.g., acid rain, that the first laws for environmental protection were enacted in England. Treatment of the obnoxious gaseous, liquid, and solid wastes of the process resulted in new processes for the manufacture of chlorine and sulphur. Leblanc's process came to an end with the development of the Solvay process. Eventually, the discovery of huge fields of natural sodium carbonate in the U.S. led to the decline of the Solvay process. Up to the middle of the eighteenth century potassium loom and manufactured from cotton, hemp, and linen carbonate (vegetable soda) and sodium carbonate fibres, had a grey colour and were bleached by (mineral carbonate) were obtained from natural primitive methods. The first stage involved repeated deposits or from the ashes of certain plants and washes with stale urine, potash, sour buttermilk, or seaweed. Ashes were produced from wood (potash or sulphuric acid, and the cloth was then laid out on th e pearl ash) imported from Eastern Europe and the sunlight for three to sixth months. The process was Colonies; from seaweeds (kelp) growing in Scotland, very lengthy, depended on the weather and utilized Ireland, Norway, and Northern France, and from vast areas of land that could not be cultivated. By the Salsola soda (barilla) , a salty plant growing in the end of the eighteenth century notable improvements Mediterranean coast of Spain. The two carbonates of the bleaching process came into being with the were an essential raw material for three growing discovery of the bleaching properties of chlorine by industries: it was used in the textile processing as an Claude-Louis Berthollet (1748-1822), and the alkaline scour in the bleaching of linen and cotton manufacture of bleaching powder. Later on, it was cloth; in glassmaking as a fluxing ingredient to lower discovered that sulphuric acid could be used to the melting point of soda lime glass compositions; mordant indigo on wool. Indigo, one of the most and in soap-making. Development of synthetic popular dyes of all times had previously been methods for manufacturing sodium carbonate may be colourfast only on cotton and linen (Note I). considered as the catalyst led to the chemical Nevertheless, the limited amounts of sulphuric acid revolution. Synthetic methods provided the answer to and chlorine available and their relatively high values the economic bottleneck created by limited supplies did not allow use of these techniques for the mass of the traditional raw materials. In the beginning, production of white clothes. increased imports provided partial release to the Leblanc's development of the synthesis of sodium scarcity problem, but the political situation and carbonate from common salt led eventually to a expanding economy of Europe made this alternative substantial decrease in the price of soda and chlorine. short-lived. the latter obtained from the by-product hydrogen A good example of the problems involved is that of chloride. Not only that, the synthesis released the the bleaching processes employed by the textile industrialized countries from the need to import the industry before the synthesis of sodium carbonate was chemical and be a servant of other countries. achieved. The different fabrics coming out from the Development of sodium carbonate as a major chemical commodity is interesting because of the *For correspondence: wi sniak @bgumail.bgu.ac.il stages it went through; first, exploitation of natural Educator Indian J. Chern . Techno!., January 20m resources, followed by chemical synthesis, and a between Alexandria and Rosetta, he "saw here and return to the use of natural resources in the twentieth there a few unhusbanded Palmes, Capers, and a weed century. called Kall by the Arabs. This they use for fuel and We will now describe these three stages and the then collect the ashes which crusht together th ey sell social, political, economical, and industrial events that in great quantities to the Venetians; who equall y accompanied it. mixing the same with stones make thereof their crystalline glasses". Natural resources When the Arabs settled in Spain about the seventh Natural deposits of sodium carbonate have been century, they substituted the soda resources available known and used from ancient times. In Book XXXVI in northern Africa by the cultivation of a sea shore of hi s "Natural History", Pliny writes about the plant, to which they gave the name kali or alkali, discovery of glass by a "mercaturum nitri" (merchants probably derived from the Hebrew root meaning to 2 of nitre): "There is a story that once a ship belonging burn . After expulsion of the Arabs, th e Spaniards to some traders in natural soda put in here and that changed the name of the plant to bariglia in the XV II they scattered along the shore to prepare a meal. century and to barilla in the XVIII century. 2 Since, however, no stones suitable for supporting their According to Patterson , it is reasonable to assume cauldrons were forthcoming, they rested them on that the Arabs also manufactured alkali by charring lumps of soda from their cargo. When these became the argol or tartar (potassium hydrogen tartrate) that heated and were completely mingled with the sand on precipitated in wine casks. the beach, a strange translucent liquid flowed forth in In the old days, the words natrum, kali, and soda streams; and this it is said, was the origin of glass'". were used without distinction. In the thirteenth According to Patterson2 in the north of Africa, century the name sal nitri came to be used for south of Tripoli , there are vast deposits of a double potassium nitrate, in place of sal petrosum, and thi s sal t of sodium carbonate and sodium bicarbonate, was shortened into nitrum and ultimately became Na1COJ.2 NaHC03.2H20 , not being commercialised nitre, in English; but the words kal i and natron today. The Egyptians probably knew of them, and continued to be used indiscriminately for potassium 2 also the Israelites, who called it nether. According to carbonate or sodjum carbonate . the Encyclopaedia Biblica3 the material was called Sodium carbonate and potassium carbonate became neteru by th e Accadians, nitri by the Egyptians, and differentiated clearly only in th e seventeenth century vtrpov (nitron) by the Greeks. Later on, the Arabs after Henri Louis Duhamel du Manceau ( 1700- 178 1) call ed it natron, which became shortened to tron and and Andreas Sigmund Marggraff ( 1709- 1782) trona. All th e different names were simply vanations determined their properties. of the Egypti an name meaning clean, real. Old We will now discuss the different natural sources 1 Egypti an documents from the 18 h dynasty indicate in more detail. th at nitri was present in natural fields located in Wadi Natural deposits- Soda forms part of the elements Natrun, next to Naukratis in the Delta, and near EI­ of a large number of mineral sources. It is present in Kab, in Upper Egypt. The ancient Egyptians exported the mineral waters of Karl sbad, Burtscheid, and the salt to many countries and the beli evers used it to Vichy; in the water of geysers in Iceland ; as clean their mouth by chewing it wet, as a component efflorescence in volcanic rocks, trasoite and egneys of the incense fire, and also as a component of (such as Bilin in Bohemi a). In Hungary sodium mummifying materials. carbonate effloresces during the hot season in the 5 The word nether is mentioned twice in the Bible, in form of a crystalline crust, called Szekso • both cases in relation to its cleansing properties Efflorescences or crusts originate during periods of (Note 2). hot weather from the partial or total evaporation of The ancients also knew that the ashes obtained by lakes without outlets, or from evaporation of the soil bu rn ing seaweed and land plants had properties very humidity that ascends to the surface by capill ary similar to those of the natural material. Plant ashes forces. The sodium carbonate present in salt lakes were at one time produced in Egypt and other probably originates from the reaction between sodium 4 countries. As quoted by Lucas and Harris , the chloride and calcium carbonate. It is likely that the explorer G. Sandys wrote in 1610 that when travelling initial stage is the reduction of sodium sulphate to 100 Wi sniak: Sodium carbonate Educator sodium sulphide, under the influence of organic developed a system for accumulating water to avoid substances. The sulphide is then transformed into the decrease in osmotic potential caused by the carbonate under the action of carbon dioxide increased salt concentration. dissolved in water. When these waters accumulate in Plants resistant to high salinity belong mainly to lakes without outlets and having a large rate of the genus Salsola, Salicornia, Atriplex, Statice. evaporation, they may produce a crust containing Chenopodium, and Fucus. The predominant species in sodium carbonate, particularly as sesquicarbonate, Spain is Salsola soda, and are usually called barillas. Na2C03.2NaHC03.2H20. In France the corresponding variety belong to the The oldest and best-known natural fields of sodium genus Salicomia and the product is called soda of carbonate are those located in the basin of Wadi salicor or Blanquette.