Page:Proceedings of the Royal Society of London Vol 60.djvu/374

Rh and Osborne* in studying the proteids of maize. The method was rendered more accurate by Hewlett,! who substituted a bath of codliver oil for the water bath usually employed as the heating medium, and exhaustively dealt with the adverse criticisms made by Haycraft and Duggan.£

I have applied this method, using an oil bath, in the examination of the proteid like colloids synthesised by Professor Grimaux and myself. As pointed out in a previous section, in the entire absence of salts these substances do not coagulate, even when boiled. Por the sake of comparison the following experiments were performed, so as to satisfy the following conditions:—(a) A 2 per cent, solution of the substance under examination was always used. (6) The diluent fluid always consisted of a 075 per cent, solution of sodium chloride, (c) In each experiment 10 c.c of the fluid under examination was used, and the test-tubes, were of uniform internal diameter. By this means the mass to be heated remained constant. The thermometer was placed in the middle of the test-tube containing the fluid under examination.

The colloid A (“ collo'ide amidobenzoique ” of Grimaux) shows a coagulation temperature of 70° to 71° C.

The colloid B (of Grimaux) which is prepared from the same reagents as the colloid A, but the temperature at which the reaction of synthesis is conducted is allowed to rise to 130° C., shows on heating one faint appearance of flocculi at 56° to 58° C., and a second more pronounced coagulum at 70° to 72° C.

The colloid C (“ colloide aspartique ” of Grimaux) on fractional heating shows three distinct sets of flocculi, appearing respectively at 58°, 67°, and 737° to 76*4° C.

The colloid a, if cax-e has been taken to keep the temperature of preparation constant at 125° C., shows, on heating, only one coagulum at 70'6°; if, however, in the preparation of this colloid the temperature of synthesis is allowed to rise, a second colloid coagulating at 42° C. is often but not always formed.

The colloid /3, even when the temperature of the synthesis has been kept constant at 130° C., shows, on heating, three constituents coagulating at 47° C., 56° C., and 74° C.

The colloid 7 apparently only has one temperature of heat coagulation, viz., 75° C. The colloid 6 coagulates at 75° C. The colloid e coagulates only at 47° C. The colloid £ coagulates at 48° and 59° C.

t Hewlett, ‘Journ. Physiol.,’ vol. 13, p. 493, 1892. X Haycraft and Duggan, ‘ Brit. Med. Journ.,’ 1890, vol. 1, p. 167; ‘ Edin. Roy. Soc. Vroc.,’ vol. 16, p. 361, 1888-9.
 * Chittenden and Osborne, ‘ Amer. Chem. Journ,’ vol. 13, 7 and 8; vol. 14, 1.