PROGRESS OF CHEMISTRY IN SOUTH LANCASHIRE. 123 



plan, which consists in passing the sawdust into the retorts by means of an 

 inclined plane, and a series of scrapers. 



Quantity of acid manufactured weekly in Manchester: — 12,000 gallons, 

 containing about 4 per cent, of glacial acid. 



The value of the acid is £3 per ton, whilst that of the tar is from £4< to 

 £4^ 10s. 



The quantities of red liquor (acetate of alumina) and iron liquor (prot- 

 acetate of iron) made may be stated here, as they are always made by means 

 of pyroligneous acid, and generally by the same parties who manufacture the 

 acid. Red liquor, 12,000 gallons. Iron liquor, 6000 gallons. 



XX. Starch and Artificial Gums. 



About 20 tons of starch and 34 tons of gum-substitutes, made by roasting 

 farina and other kinds of starch, are produced in this district per week. 



No change has taken place in the process of manufacturing starch from 

 flour. The old process of fermentation is still adhered to. 



XXI. Purification of Kesin. 



Several very interesting and successful processes have lately been patented 

 by Messrs. Hunt and Pochin of Salford, for the purification of resin. The 

 aim of these gentlemen, who have devoted a large amount of time and atten- 

 tion to this subject, is to produce a bright, nearly colourless, solid and brittle 

 resin from the common dark and impure commercial article. This end 

 they attain by distilling the resin in an atmosphere of steam at about 10 lbs. 

 pressure. The several resinous acids which on distillation by themselves 

 split up into gaseous products and volatile oils of very variable composition, 

 are mechanically carried over, it would appear, in presence of steam, as is 

 well known to be the case with stearic and the other higher fatty acids ; and 

 a solid product, which cannot be distinguished from the finest resin, is 

 obtained from a very impure material. In their patent of 1858, Messrs. 

 Hunt and Pochin specify the formation of three distinct solid products 

 during diff"erent stages of the process ; these they distinguish as a, /3, and _ 

 y resin. These three several substances present the characteristics of resins, 

 but clarified and to a great extent deprived of colour. They are either 

 separately or in combination applicable to and useful in the manufacture of 

 several important articles, such as soap, size, candles, paper-size, varnish, 

 and japan ; and they may be used for distilling to produce resin-oils. 



About 60 tons per week of this purified resin are now manufactured in 

 this district under this patent. 



XXII. Organic Colouring-Matters. 



There are few substances of more importance to the manufacturers of this 

 district than those which are employed in imparting colour to the various 

 fabrics, especially those of cotton, produced here. Of these substances the 

 majority are derived from the animal or vegetable kingdom. Indeed, with 

 the exception of oxide of iron and chromate of lead, very few mineral sub- 

 stances are at the present time made use of alone by the dyer or printer. 

 The greater intensity, beauty, and variety of the dyes which are wholly or 

 in part composed of organic matters causes them to be preferred ; and the 

 increase of skill and knowledge of scientific principles on the part of dyers 

 and printers has also led to their more exclusive employment. When it 

 is stated that the quantity of dye-woods (logwood, peachwood, sapanwood, 

 barwood, fustic, quercitron bark) consumed weekly by the dyers of this 



