1886.] on Becent Progress in the Coal-tar Industry. 463 



and its chemical name is benzoyl sulphonic imicle, or for common 

 use, saccharine. It does not act as a nutriment, but is non-poisonous, 

 and passes out of the body unchanged. The following is a concise 

 statement of its properties, and mode of production from the toluene 

 of coal-tar. It should, however, be first mentioned that the compound 

 benzoyl sulphonic imide (saccharine) was first discovered by 

 Constantin Fahlberg and Eemsen, in America. But no patent was 

 taken out for a commercial process till recently, and it is now 

 patented in this country. 



Step I. — Toluene is treated with fuming sulphuric acid in the 

 cold, or it is heated with ordinary sulphuric acid of 168^° Twaddell 

 on the water-bath, or not above 100° C. The latter method is the 

 better. The acid is best caused to act upon the toluene iu closed 

 vessels rotating on horizontal axles. 



CeH,CH3 + SO,U, = CoH, {go^ OH + H,0. 



Toluene. Toluene sulphonic acids 



(ortbo and para). 



Step II. — After all toluene (which as toluene is insoluble iu the 

 acid) has disappeared, the contents of the agitating vessel are run 

 into wooden tanks iu part filled with cold water, and the whole liquid 

 is stirred up with chalk to neutralise the excess of sulj)huric acid used 

 and to obtain the two isomeric toluene sulphonic acids as calcium 

 salts. 



K^«^^ !sa . oh) + ^^^^2 + 2(CaC03) = 



Toluene, ortho- and 

 para- sulphonic acids 



(c«Hi^^^A^C.^ + CfiSO, + 2CO2 + 2H2O. 



Calcium toluene ortho- 

 and para-sulphonates 



The neutralised mass is filtered through a filter-press to separate 

 therefrom the precipitate of gypsum, which is washed with hot 

 water, and the washings added to the filtrate. 



Step III. — The calcium salts are now treated with carbonate of 

 sodium, to obtain the sodium salts, with precipitation of carbonate 

 of calcium. The precipitate is removed by means of a filter- 

 press from the solution containing the sodium ortho- and para- 

 sulphonates. 



(c.H,{CH3),Ca + NaXO, = CaCO, + 20,H,{2^^ ^^^ 



The sodium toluene sulphonates 



Step IV. — The solution of the sodium salts from III. is evapo- 

 rated either in an open- or in a vacuum-pan so far that a portion taken 

 out will solidify on cooling. The contents of the pan are then run 



Vol. XI. (No. 80.) 2 h 



