175 



salt and afterwards in a sesqui-oxide of iron or peroxide. These are 

 finished in bi-chromate of potash and alumina. Sulphate of potash has 

 been recommended. I would prefer to use (if using salts metallic) 

 the nitrate of sodium. The salt found in South America is preferable. 



The combination tannages of England originated, I think, in the 

 town of Warrington, and also in the neighborhood of .Leeds. In War- 

 riugton the combination consisted of mixing potash and sulphuric 

 acid together in the first liquors and finishing in divi divi, myrabolams 

 and valonia. Vacuum tan-pits were also in use by some tanners of 

 this place, which were, I think, eventually relinquished. At Joppa, in 

 the vicinity of Leeds, the combination consisted of mixing terra ja- 

 ponica and sumac together in conjunction with sulphuric acid; the _ 

 pelts which were chiefly E. I. kips, were also bated or drenched in a 

 peculiar manner, the excrement of hogs being used as a drench, and 

 before they were exposed to the action of the lime they were softene^d 

 in an ammoniacal liquor made from nitre, blood, a.nd the exuvia of dogs. 

 There is to-day scarcely a pure oak-bark tannage in the country 

 all are combinations to a greater or less extent. 



We will commence with the 



. LIMING PROCESS. 



Calcium is found in prolific abundance in almost every part of the 

 world ; its uses are multifarious and the history of its usefulness is 

 found in the oldest records in the ruins of Pompeii as well as in the 

 most recent buildings of modern times. 



As a caustic alkali it has the property of decomposing every descrip- 

 tion of animal and vegetable fibre ; it is this property that renders it 

 so serviceable to the tanner, inasmuch as it attacks the fibre of the 

 hide, whilst its alkaline character saponifies the fatty and nitrogene- 

 ous matter, thereby setting free the ammonia, which in its affinity for 

 sulphur attacks the hair bulbs and performs the depilatory process. 

 It is soluble in water at about six hundred times its weight. 



The anatomy of the hide, the general formation of the hide, consists 

 of a network of fusiform cells, divided into distinct parts, called by the 

 physiologists the epidermis or scurf skin, the cuticle or true skin, and 

 the fibrous membrane ; its chemical constituents are nitrogeneous, 

 with a modicum of sulphur. The latter is found principally in the 

 hair; it may be described as gelatine, which is N. or nitrogen, fibriue, 

 N. S., or nitrate of sulphur; hence when brought into contact with 

 milk of lime, hydrogen forms an affinity with nitrogen and lime, hence 

 ammonia, N. H. 3; this attacks sulphur and thus the desired result is 



obtained. 



Old limes become Nitrate of Calcium, N. 05, and saponaceous, and 

 as in this state it is very deleterious to the hide, you will therefore 



