180 farmers' and mechanics' journal. 



together; and, finally, a sufficient quantity of water is added, to in- 

 crease its volume to 17 1-2 litres,* which will produce 70 bottles 

 of blacking, of a quarter of a litre each. This blacking is some- 

 times scented with an essential oil, such as that of rosemary, &c. 



The mixture must be constantly agitated, while putting into the 

 bottles, in order that the heavier or lighter parts may not separate 

 from each other. This blacking, when it is sent to any great dis- 

 tance, or remains long in the shops, is susceptible of entering into 

 fermentation ; and the great quantity of carbonic acid formed, dur- 

 ing the conversion of the saccharine matter (the melasses) into 

 alcohol, exerts a pressure in the bottles, and renders them liable 

 to burst ; or, when the cork is drawn, to occasion the effervescing 

 liquid to fly out ; to prevent which, it is sufficient to cause the 

 corked bottles to be boiled in water for half an hour, in M. Appert's 

 mode ; but it is probable that the same end may be accomplished 

 by mixing a small quantity of the sulphurous acid with the black- 

 ing. Whenever the blacking is to be used, it must also be shaken 

 or stirred up, in order to mix those parts again, which are apt to 

 separate on standing. 



This composition is effected by the re-actions of the sulphurous 

 and hydrochloric acids upon the ivory-black ^ also, by the hydro- 

 chlorate, the sulphate and the phosphate of lime formed, the car- 

 bon, and the other ingredients employed in its preparation ; which 

 sustain very little alteration from their mixture. This composi- 

 tion being spread upon the leather, and rubbed over, while it is 

 wet, with a rather hard brush, makes it acquire a beautiful, bril- 

 liant, and black polish ; it adheres closely to the leather, and is not 

 removed by any slight friction, not even in damp weather. The 

 hydrochloric or muriatic acid, which ia employed in an equal quan- 

 tity, or is about a third-part of all acids used in the composition, 

 forms with the lime a soluble deliquescent salt, which enters and 

 gives a softness to the leather, and does not produce that dull ap- 

 pearance which results from an excess of the sulphate of lime. 



This article forms a very important branch of commerce in Eng- 

 land ; considerable quantities of it being exported ; and, in the 

 large manufactories, steam-engines are employed in its preparation. 



Some years since, I pointed out a more economical mode of 

 making a blacking, which is yet equally beautiful with the above : 

 it consists in substituting for the melasses and gum, either the fecula 

 of potatoes, or the potatoes themselves, saccharized by the action 

 of the sulphuric acid ; and for the ivory-black, animal or bone char- 

 coal, ground in water. It is made in the following manner : sup- 

 posing all the ingredients, except those substituted, to be used in 

 exactly the same proportions as we have above given : 



Either the fecula, or the potatoes, after being boiled and crush- 

 ed, so as to be reduced to a gelatinous state, are to be mixed with 

 tepid water (at about 45° ;) and sulphuric acid, previously diluted 

 with ten times its weight of water, is then poured on it by degrees, 

 and the whole brought to a boiling heat in a leaden vessel ; being 



* The litre is nearly equal to 5J 1-2 wine pints. 



( 



