1888 - 89 .] Haycraft and Duggan on Coagulation by Heat. 363 
rapidly the temperature may materially increase above the point 
at which, were the fluid kept for a sufficient time, coagulation 
would occur. Although our experiments convince us of the general 
truth of this fact, it occasionally happens that an albumen slowly 
heated coagulates at a very high temperature, and perhaps never 
forms distinct flocculi, the coagulation being in the form of a thin 
jelly. Another portion of the same solution quickly heated 
coagulates in flocculi at a lower temperature. "We have found this 
occur with some specimens of serum albumen. We are inclined to 
explain this occurrence on the supposition that the slow and 
continuous heating in these cases causes some chemico-physical 
change in the albumen itself, whereby its coagulation is affected. 
The Influence on the Coagulation Point of the Degree of Concen- 
tration of the Albumen itself 
We find, as the result of our experiments, that in all the 
albuminous solutions we have investigated, the coagulation point is 
considerably raised by diluting the solution. A very dilute solution 
may not coagulate even on boiling, and egg white, diluted, but 
nevertheless forming a comparatively strong solution, cannot be 
coagulated, as Sir William Roberts long ago pointed out. 
In our experiments we invariably proceeded in the same way as 
regards the rapidity with which the solutions were heated, so as to 
eliminate any fallacy which might arise on this score. The usual 
method for determining coagulation points was adopted. The 
solution was placed in a test-tube containing a thermometer which 
could be used as a stirrer. The test-tube was immersed in a water- 
bath consisting of two beakers, one within the other, and each one 
filled with cold tap water. The water-bath was heated by a 
Bunsen, the flame of which was kept always at the same height, and 
so arranged that it took some forty minutes for the fluid in the test- 
tube to reach the temperature of 80° C. All our experiments were 
performed in this way, so that uniformity of results was obtained. 
We are inclined to think, however, that the heating process was 
unnecessarily slow, not only on account of loss of time, but what is 
more important, because it permitted changes to take place in the 
albuminous solution, especially when acids or alkalies were present 
in the fluid. 
