100 
The N.Z. Journal of Science and Technology. 
[June 
fatty acids, some of tliese fatty acids being solid and some liquid. 
Depending upon the proportion of solid and liquid fatty-acid compounds, 
a fat is hard or soft. Thus in the titre test the fatty acids of the tallow 
are separated out by themselves, and by suitable means, with the aid of 
a carefully tested thermometer, the temperature at which the mixture of 
fatty acids becomes solid is determined, and so its hardness is indicated. 
In general the hardness of a tallow is beyond, the control of the tallow- 
manufacturer, for it depends upon the breed, age, sex, and part of the animal 
from which the fat was removed, and to some extent upon the food ; thus 
mutton-fat is normal!v harder than beef, that from mature animals is 
harder than that from the younger, the fat from the male is generally 
harder than that obtained from the female, the caul and kidney fats are 
harder than those from the breast, while animals fed on grass yield a 
harder fat than those fed upon oil-cakes or brewery-refuse. 
The colour of a tallow is to some extent under the control of the 
manufacturer, for by a careful selection of the materials and the washing 
of certain classes of offal (especially the paunches), and by removing the 
undigested food, it is possible to secure a measure of cleanliness which 
goes far in obtaining a tallow which will not be unduly dark in colour. 
Faulty rendering of the material in the digester is also a common source 
of discoloured tallow ; a high and prolonged pressure (and its equivalent 
temperature) disintegrates substances which, either in a fine state of 
suspension or by actually becoming dissolved by the fat on heating, 
produce a high colour. 
The amount of free fatty acidity in tallow varies considerably, and 
is a measure of the freshness and proper rendering of the fats. As has 
been stated above, fats are definite compounds of fatty acids and glycerine, 
and as such in a fresh state are practically neutral ; but if for any reason, 
either because of decomposition due to delay in handling, or on account 
of unduly high temperature in rendering, the fat splits in part into its 
components glycerine and fatty acids, then the fatty acids are free and the 
fat is no longer neutral. 
The presence of moisture and detritus in more than small amounts 
is indicative of faulty methods of refining and the imperfect breaking-up 
of emulsions in the refining and settling kettles. 
The following results indicate the characteristics of tallows and of 
neat’s-foot oil :— 
Table V. 
Specific gravity at 65° F. 
Melting-point (° C.). . 
Titre (° C.) 
Saponification value 
Free fatty acidity .. 
Moisture 
Detritus 
Tallow. 
Mutton. Beef. 
Neat’s-foot Oil. 
0-937-0*953 
42- 49° 
43- 46° 
192-195 
0-952 0-916-0-917 
41-48° 
43-45° 26-27° 
194-198 194-197 
Varies 0-5-5-0 per cent. 
„ 0 - 2 - 1-0 
„ 0-1-0-5 
0-2-3 per cent. 
0 - 1 - 0 - 5 ^ „ 
0-10-5 „ 
Uses .—Rendered tallows of all grades are used for many purposes, 
chiefly for soap and candle making and for lubricating. Neat’s-foot oil is 
used largely as a soap emulsion for treating hides and skins in leather 
industries ; also for lubricating. , 
