Remarks on the Crude Sodas of Commerce. 47 



into the cause of this, in order to ascertain, whether the evil 

 complained of by our manufacturers, might not be remedied. 

 My attention was naturally first directed to the difference of 

 the two manufactories ; the following are the principal points 

 of difference. In France, soap is generally made from soda 

 and olive oil; it is colored, and that most sought after is called 

 bleu pale. In this country, we generally use the animal oils, 

 and in all but the very fine soaps, our manufacturers are in 

 the habit of using a considerable proportion of rosin ; the 

 most saleable of this kind of soap, is of a bright yellow 

 color. In France, the soap is marbled, by adding to it while 

 in a mass, a solution of green vitriol, sulphate of iron. Now 

 it appears, from the statement of M. Laurens, who is prac- 

 tically acquainted with the subject,* that in order to impart 

 to the soap the precise tint, so much sought after, the bleu 

 pdle, the presence of the sulphuretted hydrogen, or rather 

 of the alkaline hydrosulphuret, (for both of the alkalies are 

 found to answer the purpose,) is indispensable. In this pro- 

 cess, the sulphuretted hydrogen, when united with the iron 

 and oil, imparts a greenish blue color, which does not com- 

 bine with the soap, but is dispersed through it, during ebulli- 

 tion, in small masses, so as to produce the marbled appear- 

 ance. M. Laurens remarks, that the more scientific man- 

 ufacturers at Marseilles, are in the habit of adding sulphur- 

 retted hydrogen, after treating the soap with the green vit- 

 riol, should it not be found to possess the proper color. This 

 seems to afford a ready, and natural solution of the fact, that 

 artificial barilla is used with advantge in the soap manufac- 

 tories of France, while in this country it is so objectionable. 

 I have had recourse to a number of experiments with differ- 

 ent substances, for the purpose of devising a cheap method 

 of getting rid of the sulphur, combined with artificial soda, 

 so inconvenient to our soap makers, but without arriving at 

 any very satisfactory results. Some advantage may be ob- 

 tained if the ley be introduced into open vats, into which 

 the clippings of tin plate, or iron have been thrown, and left 

 standing exposed to the air, for several days, and occasion- 

 ally agitated. 



Economy of materials is the basis of successful manufac- 

 turing, and, as the intrinsic value of the crude sodas depends 

 entirely upon the quantity of pure alkali they contain, the 



* See Ann. de Chim. v. 67. 



