IMPURITY AND MANUFACTURE OF SODA» ^3 



in the state in which they had been taken out of the evapo- 

 rating vessel, a brisk effervescence took place, arising from 

 the extrication of carbonic acid and sulphuretted hidrogen 

 mixed. Willing to satisfy myself whether the formation of This not forre- 

 hidrosulphuret of soda had not taken place during the boil- foiling, 

 ing of this alkali to extract the carbonate, 1 took 3gr. [46grs] 

 of powdered soda, put them into a phial, and poured on them 

 muriatic acid. This produced a brisk effervescence, and a 

 very strong smell of sulphuretted hidrogen gas. On passing 

 tiiis gas, by means of a tube, through several solutions of 

 metallic salts; the oxides were precipitated of the same co- 

 lour as they would have been by sulphuretted hidrogen gas 

 obtained from the decomposition of sulphuret of iron by- 

 sulphuric acid. 



From a mixture of crystallized tartarous acid in powder Suip^^urettea 

 and soda sulphuretted hidrogen gas was equally evolved, i^idrogen 

 ^, . , . I , . ,, . evolvedfroTn 



Inese experiments were made with the various sorts sold m various speci> 



the shops under the names of Carthagena soda, kelp, and n^ens. 



barilla. They all presented the same results. 



It cannot lae doubted therefore, that the hidrosulphuret Crude soda al- 



of soda is contained in all the kinds of soda ; and that it may ^^y^,'^^"!^'"* 



. . •' mated with 



be obtained from the mother waters of the lixiviums, that hidrosulphu- 



have furnished carbonate of soda. The formation of this salt ^^^' 

 is easily understood. When the plant is burned for procu- Source of it, 

 ring the alkali, the fire is urged so far as to cause the ashes 

 to undergo a semivitrification : the sulphates contained in 

 them are decomposed by the action of the charcoal : the sul- 

 phur is liberated and forms sulphurets. At the same time 

 there is an extrication of hidrogen gas, which may be furn- 

 ished by the charcoal itself, or by the decomposition of the 

 plant or of water ; and no doubt by the three together. This 

 hidrogen gas, uniting with the sulphur, constitutes the sul- 

 phuretted hidrogen gas, which in its turn combines vpith a 

 part of the alkali, and forms hidrosulphuret of soda. 



The formation of the sulphurets and hidrosulphurets that Thepreparr 

 barilla contains being occasioned by the strong calcination ^'^^" °'^* 



^f the ashes furnishing this alkali, we may infer, that the 

 piethod of preparing it is defective. It is evident, that part Inconvenien-. 

 of the alkaline salt enters into the const tution of the sul- *^^ °^'*» 

 phuretsand hidrcsqlphurets contained in it. These remain 



ia 



