German Method of Manufacture. —The following details of the modern process adopted in South Germany, obtained from a very reliable source, are not without a considerable degree of interest.
The conduct of the manufacture may be divided under two beads : L The making of the tartrate of lime ; 2. The production of the tartaric acid fl om the salt. The raw materials consist of crude tartar, wine lees, and the residue from the manufacture of Rochelle salts and tartar refining.
1. Making the Tartrate of Lime (a) from Crude Tartar.— Raw tartar 10 to 15 cwt., according to quality, is put into a vat of sornc 2200 gallons capacity, four-fifths filled with water. The water is heated by steam nearly to the boiling point, during which time it is kept in motion by a revolving spindle. When this temperature is reached, the steam is cut off, and the free part of the tartaric acid neutralized, for which purpose powdered chalk may be used. This settles out as tartrate of lime, and the easily soluble neutral tartrate of potash remains in solution. Carbonic acid escapes iu streams, for which reason abundant ventilation must be provided. Theoretically, this reaction requires that for 18.8 parts of tartar there shall be 5 parts of chalk ; as, however, the crude tartar seldom contains more than 80 per cent. of acid tartrate of potash, this proportion is not found to be necessary in 'intake. Further, it is not imperative to completely neutralize, cause the magnesia, clay, oxide of iron, ate., which might be very troublesome in subsequent operations, then fall out as •(Ii. It is even advisable, when the tartar is very rich in such matters, or in colouring bodies, to laid 25 to 5u lb. of muriatic acid at the beginning of the operation, and yet not altogether to neu tralize, on account of the subsequent formation of Epsom salt and alum.
For converting the tartrate of potash into tartrate of lime, gypsum is best suited, as this salt is generally much cheaper than chloride of limp. The quantity of gypsum necessary may be calcu lated from the amount of chalk used, 5 parts of chalk = 8.6 parts of gypsum. Of course it makes no difference whether the gypsum be added previously or during the neutralizatiou by the chalk, neither will any harm arise from an excess of it.
As the tartrate of lime extracted from the lees is very dean and, on conversion to tartaric acid, leaves a very dean gypsum as a bye-product, in many works the gypsum thus produced is preferably used for turning the tartrate of potash into tartrate of lime. The reaction of the gypsum on the neutral tartrate of potash manifests itself slowly and requires several hours, e,pecially if the liquid be very concentrated. In order to see if the reaction be finished, a cooled sample is filtered and decomposed with acetic acid. When a precipitate is no longer given the rcactiou is tiuished.
When this point is reached, the contents of the vat are cooled to about 50' (122' F.) and run into another vessel, for the deposition of the tartrate of lime, which is allowed to pass through a sieve to retain the foreign bodies accidentally present in the crude tartar, as wood chips, dust and pieces of molten sulphur. After three or four hours the fluid is cooled down to about F.), and the tartrate of lime deposits itself, so that the supernatant liquid can be syphoned off.
A triple washing is generally sufficient to make the tartrate of limo pure enough for further operations. In the first ley which is drawn from the tartrate of lime much sulphate of potash is found, which may be recovered if the needful plant be at hand and the market vtduc will repay the cost of evaporation.
(b) Front Mite Lecs.--In the spring following the principal fermentation of new wine, the wine is drawn off from the deposit that has formed, which will amount to about five per cent. of the quantity of the wine. This residue may he pressed and will yield about 8 of its bulk us so-called press wine, which, in Austro-Hungary for instance, is coloured with cheap dark led Dalmatian w ins and mixed with the requisite quantity of glycerine, and is very largely drunk. About will be left behind as a dough-like lees. Formerly this lees was only used as a manure, for which it is valuable as possessing potash salts and phosphates. Probably Mr. E. von Seibel, at Licsing, near Vienna, was the first to utilize the tartrates (7 to 20 per cent.) in lees for the production of tartaric acid, and many manufacturers have followed him.