There is an important difference in the value of the European and American products. The proportion of tannic acid in the latter exceeds that found in the former by 6-8 per cent., yet the former is much preferred by tanners and dyers. By using Sicilian sumach it is possible to m ike the finer white leathers, so rnuch uaed for gloves and fancy shoes ; while by the employment of the American product, the leather has a disagreeable yell )vi or dark colour, apparently due to a colour ing matter, which, according to Loewe, consists of quercitria and quercetiu, and exists in larger quantity in tho American than in the Sicilian.
The experimental results obtained by collecting sumach at different seasons were : Virginia, mixed, collected in June, gave 22.75 per cent. of tannic aeid.
27 77 July, 27.38 R. glabra August, 23.56 R. copallina 16.99 If SiCilian, R. Coriaria 24.27 It is evident, therefore, that in order to secure the maximum amount of tannic acid, the sumach should be collected in July, but the colouring tnatter of the leaves haa an important influence upon the value of the product. The leaves of the upper extremities of the stalks are always richer iu tannic acid than those of the base; and the increase of age of the plant is aecompanied by a general diminution of thia acid. Yet the collection of the crop ahould be layed as long as poasible, because the diminution of tannin iu the leaves will be abundantly compensated for by the quality of the product.
Experiments upon the presenee of colouring matters were made by treating gelatine solutions, and gave the following reaulta : Virgiuia, mixed, collected in June, gave .. A nearly white precipitate.
July, .. A decidedly yellowish-white precipitate.
R. copallina, August, ., .. A dirty-yellow precipitate.
R. glabra, 92 77 72 . A very dirty-white precipitate.
Fredericksburg mixed, .. A dirty-yellow precipitate.
Sicilian .. A slightly yellowish-white precipitate.
It is therefore advised that for the purpose of tanning white and delicately-coloured leathera, the collection should be mad() in June ; while for tanning dark-coloured leathers, and for dyeing aud calico-printing in dark colours, where the slightly yellow colour will have no injurious effect, the collection be made in July. It appears that fur all purposes, the sumach collected after the 1st of August is inferior in quality.
Fig. 1426 shows a mill for grinding sumach-leaves; it omelets of a heavy solid circular wooden bed a, 15 ft. diam., with a depression around the edge b, a few inches deep and 1 ft. wide, for the
reception of the ground sumach from the bed, and 2 edge-rollers r, weighing about 2500 lb. each, 5-6 ft. diam., and provided with numerous teeth of iron or wood, thickly inserted. Most mills have to be stopped to allow the unloading of the bed, but this delay is obviated by an apparatus consist ing of an angular arm d, attached to a scraper e, and worked by a lever f, which passes through the hollow shaft g and extends to the room above, where it terminates iu a handle h. The scraper carries tho ground sumach to the opening i, whence it is taken by an elevator to a revolving sieve or scre,en in a room above. After screening, the sumach is packed in bags, 15 to the ton, being always sold by that weight. The chasers aud beds are inclosed in a case or drum, aud the grinding is done by the application of power to the upright shaft g. The mills are fed from above. The packing is sometimes done by machinery alone. The best mills cost about 600/. In Europe, and in aome parts of the S. States, sumach is still ground by stones revolving on a atone bed, and the sifting is often done by hand.
E. Coez & Co., St. Denis, near Paris, make a sumach extract. It is concentrated to a syrupy consistenoe in a vacuum-pan, and keeps well, exhibiting none of the acidity which is manifested by a simple deeoetion of sumach leaves. Sumach eontains 16-24 per cent. of gallotannic acid, and ia somewhat similar in tanning properties to myrohalans, but paler in colour. It is priucipally used for tanning morocco and other fancy leathers.
The district of Ancona yields 200 tons per annum of sumach, said to be equal to and cheaper than the Sicilian, but mostly consumed locally. Palermo exported of " ventilated " sumach to the TJnited States 120,043 bags (14 = 1 ton) in 1877, and 50,085 in 1878, the average value being 14/. a ton. Trieste exported 7800 cwt. by land in 1877; in 1878, the shipments to England were 16,600 kilo. (of 2.2 lb.), value 1328 fl. (of 2s.), and in 1880, 91,800 kilo., 7344 fl. Rustchuk in 1880 exported 1400 tons, chiefly to Roumania and Austria. Our imports in 1880 were 10,573 tons, 133,249/., from Italy, and 1047 tons, 12,416/., from other countries ; total, 11,620 tons, 145,665/. The approximate London market value is 15s. 16s. 6d. a cwt. for Sicilian, 10 lls. for Spanish.