338 SEWAGE AND ITS PURIFICATION 



II. The Ayrshire Process (Biggart & Co., Dairy), specially 

 applicable for certain classes of wool and potash soaps. The 

 sedimented suds are evaporated, and the grease which separates 

 is removed. The residue is calcined, and yields a crude car- 

 bonate of potash, which is either dissolved and used again for 

 scouring, or refined, when it sells at £16 tos. per ton. The 

 grease is boiled with sulphuric acid, and may be sold at about 

 £6 per ton, or purified further. The process is said to be 

 worked at a profit. 



III. Kimmms and Craig's patent (adopted by Holden and 

 Sons, Bradford, i8go) ; coagulating the liquor by chloride of 

 calcium to obtain a clarified neutral liquid. 



IV. Ordinary or Sulphuric Acid Process. When the suds are 

 treated or '' cracked " with sufficient acid to decompose the 

 soaps, the grease and fatty acids rise as a dark scum and are 

 collected and filtered, pressed hot, and sold as " Yorkshire 

 Brown Grease." 



V. Mechanical or '' Battage " Process of Motte & Co., Roubaix, 

 France. The suds are agitated by beaters, raising a froth 

 which carries to the surface the globules of insoluble fats, this 

 is skimmed off by travelling scrapers and heated to 60° C. with 

 one-thousandth of sulphuric acid to clarify and separate it. 

 The grease is strained through canvas bags, and the refuse is 

 sold as manure. The acidified effluent is precipitated by lime, 

 and is then said to be neutral and perfectly clear. 



VI. Lagerie Process, Roubaix. In France and Belgium and 

 in a few cases in England (as at Alston Works, Bradford), the 

 potash and much of the organic matter is extracted by hot 

 water from the wool before scouring, and the liquor evaporated 

 and calcined as above. 



VII. Vial process. This method has special mechanical 

 arrangements for efficient sedimentation. The sludge after 

 treatment with sulphuric acid and straining is passed into vats 

 containing agitators and scrapers, and dried by steam coils and 

 finally by superheated gases. The dry residue is extracted by 

 a solvent in a vessel provided with rotating screw mixers and 

 conveyors. 



VIII. Spence process. The sewage is precipitated by quantities 

 of ferric sulphate and sulphuric acid ascertained by tests as to 

 alkalinity and impurity, the sludge further acidulated, heated, 

 pressed, dried, and extracted with a solvent. 



IX. The Cassel Process, used at Cassel, Germany, is on similar 



