On the Decomposition oj the Muriate of Soda. 29 



earths which are found in the departments of the Aisne and 

 Oise. They contain on an average for 100 parts at 30* 

 (Beaume's areometer) : 



Sulphuric acid 13 



Oxide of iron 7 



Alumina 2 



As the sulphates of iron and of alumine are not entirely 

 decomposed by calcination, since there are only about nine 

 parts of sulphuric acid which remain free, it results that, 

 for the decomposition of a metrical quintal of sea salt, there 

 must be eight metrical quintals of vitriolic waters at 30% or 

 634 kilogrammes at 40% a quantity which answers to 72 

 kilogrammes of dry sulphuric acid, or to 100 kilogrammes 

 at QQ''. 



The operation consists, 



1. In lixiviating the efflorescent vitriolic substances. 



2. In pouring them into leaden pots until they mark 40'. 



3. In concentrating them in melting pots of the capacity 

 of 100 litres down to 3 or 6 centimetres below the edges, 

 which gives for each pot about 126 kilogrammes of water 

 at 40°. 



4. Put after'.vards into each pot 20 ki!o2;rammcs of s?a 

 sail, raise the fire, and brew the mixture until the whole salt 

 is dissolved, and the matter has acquired the consistence of 

 a thick syrup. 



5. Pour the matter into wooden troughs, and throw it 

 when it has become solid into a reverberating furnace where 

 it is calcined in three or four hours. 



6. Withdraw this calcined substance, and proceed after- 

 wards to the lixiviation and concentration of the leys, in 

 order to obtain.by crystallization the pure sulphate of soda. 



As the sulphate of soda of commerce is not pure, and as 

 it covilains n)ore than 10 per c.nt. both in humidity and in 

 earthv substances and foreign salts, and as it undergoes 

 several losses in the various manipulations, we could only 

 on a large scale obiaiii about '■205 or 215 kilogrammes of 

 crystallized sulphate ol' soda per nu-trical quintal of muriate 

 of soda. 



For upwards of a year I have gone through this process, 

 in the manufactory of M. Carpcniier at Chailleret, in the 



soda is converted into siilphatc of soda. T'ni« decomposition is facilitated, 

 i-st, because llie iron, being- hijrhly (aidii{^d in the vitriolic waters, has less 

 of the (.ulpluiric acid: 2dly, bjc.iusc the iiiur.jie of soda liir.iiig been dis- 

 solved, eacli of its molecules is in contact with a uiolecule of sulphuric acid : 

 Sdljr, because the matter preserves to the end of the calcination the hum.dity 

 necessary to the extrication of the n;uriatic acid, 



departuient 



