MANUFACTURE OF CREAM OF TARTAR. 
337 
ON THE MANUFACTURE OF CREAM OF TARTAR, TARTARIC 
ACID, PARATARTARIC ACID, CARBONATE OF SODA, SUL- 
PHATE OF POTASH, ROCHELLE SALT, AND CITRIC ACID. 
Manufacture of Cream of Tartar. — One of the constituents of 
of the juice of the grape is the bitartrate of potash, which, in the 
form of what is called in commerce tartar and argol, is deposited 
in the wine casks on the commencement of fermentation, and this 
salt being but slightly soluble in dilute alcohol, the quantity de- 
posited increases in proportion as the fermentation, and consequent 
increase of spirit in the liquid, progresses. Another portion of 
the tartar or argol is obtained from the marc or mass of grape 
stalks and husks remaining after the juice has been pressed out : 
and a further portion is found in the froth or scum which rises to 
the surface of the fermented liquors. From one or all of these 
sources combined, the cream and tartar of commerce is obtained. 
For this purpose the tartar deposit or scum is placed in a copper 
full of water, and boiled for an hour or so, to dissolve out the bi- 
tartrate of potash. This solution is then filtered off into large 
coolers, where colored crystals of tartar are obtained, free from 
many of the impurities previously contained in it. These colored 
crystals of tartar are then returned to the copper, and dissolved by 
boiling in water; a quantity of animal charcoal is next added for 
the purpose of decolorizing the solution, and shortly afterwards 
some white clay for the purpose of finishing the discoloration and 
removing the animal charcoal employed. The colorless solution is 
filtered off into crystallizing vessels as before, and thus colorless 
crystals of cream of tartar are obtained. If the crystals be not 
sufficiently white, the second part of the process may be repeated. 
As, however, it often happens that these tartar deposits contain a 
good deal of tartrate of lime, the manufacturers at Montpelier have 
of late introduced some improvements in the making of cream ot 
tartar, with the view of transforming this tartrate of lime, which 
would otherwise be lost, into bitartrate of potash. To effect this, 
the matters containing tartrate of lime are boiled with sulphate ot 
potash and an excess of sulphuric acid, by which means sulphate 
of lime and bitartrate of potash are obtained. Another improvement 
lately adopted, consists in converting the neutral tartrate of potash, 
27 
