Febeuary 17, 1922] 



SCIENCE 



187 



of the interpretation to be put upon the results. 

 In the ' ' drenching process ' ' the presence of an 

 amylolytie enzyme is essential. Starches are 

 transformed into dextrin and glucoses, which are 

 subsequently fermented into organic acids. 



A critical study of bating: John Arthur 

 Wilson and GuiDO Daub. A critical study of 

 bating limed skins in the tannery has been made 

 which tends to elevate a heretofore mysterious 

 process to a scientific plane. The primary func- 

 tion of bating is to remove elastin fibers from the 

 skin prior to tanning. This is done by means of 

 pancreatin after liming, unhairing and washing 

 the skins. When a dilute solution of pancreatin 

 was employed, complete digestion of the elastin 

 was effected only when the pH value of the solu- 

 tion lay between 7.5 and 8.5, but when a more 

 concentrated solution was used, the active range 

 was extended to 5.5 to 8.5. An explanation of 

 this is given on the assumption that an addition 

 compound between the enzyme and collagen is 

 formed in increasing amounts as the pH value is 

 reduced from 8. The rate of removal of elastin 

 from calfskin is shown as a function of the con- 

 centration of enzj'me and of the time of digestion. 

 Ammonium chloride shows an activating effect in 

 concentrations up to 0.5 gram per liter and a 

 marked inhibitory effect in higher concentrations. 

 The failure of commercial bates to remove elastiu 

 from calfskin was attributed to the presence of 

 woody fibers. A comparison of bated and un- 

 bated leathers was made. The work was illus- 

 trated by five photomicrographs and four sets of 

 curves. 



The microscope as applied to leather manufac- 

 ture: FiNi Enna. 



The isoelectric point of collagen: Arthur W. 

 Thomas and Margaret W. Kelly. Eecent expe- 

 mental work in biological chemistry has demon- 

 strated that proteins are amphoteric electrolytes 

 in aqueous solution. The point of transition in 

 their amphoteric properties is known as the iso- 

 electric point, a knowledge of which is essential 

 in interpretation of their chemical and colloid 

 chemical conduct. Hides and skins consist of 

 proteins, the protein collagen predominating. It is 

 obvious that the amphoteric nature of hide protein 

 plays an important role in tanning the hide. The 

 object of this research was to determine the iso- 

 electric point of hide protein and thus contribute 

 to the chemical control of leather manufacture. 

 The experiments enumerated in the paper shcv 

 the isoelectric point to be at a hydrogen-ion con- 

 centration of 10—^' moles per liter. At acidites 

 higher than this, the hide is electropositive and 



at lower acidities, or greater alkalinities it is 

 electronegative. 



Physiological and histological observations on 

 the flayed sTcin entering into the art of leather 

 manufacture: Alfred Seymour- Jones. Before 

 proceeding with the animal skin, the tanner first 

 removes all the hair and outer skin (epidermis) 

 from the outside and all adhering fleshy matter 

 from the inside of the skin. This leaves the true 

 skin to be converted into leather. This true skin 

 consists of four distinct layers. The topmost 

 layer is the grain membrane, which varies con- 

 siderably in feel and texture with different 

 animals. It forms a connecting link between the 

 epidermis and the true skin. Just below it lies a 

 thin layer, the cutis minor, vitally important in 

 the manufacture of good leather. Below again is 

 the fatty layer, largely consisting of groups of 

 fat cells, resembling in appearance bunches of 

 grapes. The last layer is the cutis major, which 

 forms the major part of the whole skin. It is 

 composed of white collagen fibers, intertwining in 

 every direction to form a firm and inextensible 

 coat for the body. In the grain membrane and 

 cutis minor the white fibers are supported by 

 yellow elastic fibers. When, as in bating, the 

 elastic fibers are removed, these two layers be- 

 come soft and extensible, and the skin ' ' falls. ' ' 

 This is the result desired in the preparation of 

 glove leathers, kid, and the like. But it is only 

 necessary to bate these two upper layers. Since 

 there is no elastin in the two basal layers, bating 

 these latter only causes loss of valuable skin sub- 

 stance without any corresponding benefit. 



The chemistry of lime liquors used in the tan- 

 nery : W. R. Atkin. The author has extended the 

 theories of Procter and Wilson and of Loeb to 

 the alkaline swelling of hide in lime liquors. The 

 real reason why such sharpening agents as sodium 

 sulfide and sodium carbonate produce greater 

 swelling than lime alone is that the osmotic 

 pressure which causes swelling is greater for 

 sodium collagenate than for calcium coUagenate 

 at the same pH value. The smooth grain of skins 

 unhaired in limes containing arsenic sulfide is due 

 to the fact that calcium collagenate only is 

 formed. A rapid method for controlling Ume 

 liquors is described. AlkaBne swelltng is shown 

 to be exactly analogous to acid swelling, which 

 has been more extensively investigated. Certain 

 tanning processes are shown to act in a way par- 

 allel to pickling. 



The determination of tannin: John Arthur 

 Wilson and Erwin J. Keen. The authors have 

 succeeded in improving the procedure of their 



