Milk-analysis : a practical treatise on the examination of milk and its derivatives, cream, butter, and cheese / by J. Alfred Wanklyn.

  • Wanklyn, J. Alfred (James Alfred), 1834-1906.
Date:
1874
Catalogue details

Licence: Public Domain Mark

Credit: Milk-analysis : a practical treatise on the examination of milk and its derivatives, cream, butter, and cheese / by J. Alfred Wanklyn. Source: Wellcome Collection.

    23/88 (page 11)
    Another objection relative to the lactometer (which, how- ever, pertains to the application of the hydrometer to organic fluids generally) is drawn from the circumstance that a com- paratively small change in density corresponds to a great change in composition. Making total abstraction of the difficulty and uncertainty dependent on the cream, and regard- ing milk as a solution of caseine and milk-sugar, it will be seen that whereas .the specific gravity of water rises only from 1000 to 1-032 in passing into milk, the water receives 9-2 per cent, of milk solids. In other words, whilst the density goes up only three per cent., the solids go up nine per cent. It is, therefore, disadvantageous to estimate rise in solid content by rise in density. Mineral substances, when they dissolve in water, raise the density far more rapidly than organic sub- stances. The contrast in this respect is very well shown when chloride of potassium is compared with milk solids. Thus a ten per cent, solution of chloride of potassium has a specific gravity of 1-065 at 15° cent., whereas a ten per cent, solution of caseine and milk-sugar has a specific gravity of about 1-035. To be of any value at all, a specific gravity determination in the case of such a fluid as milk must be taken with extreme accuracy; and, as is well known, the taking of specific gravities with great accuracy is not by any means one of the most facile of operations, and is certainly not easier than the taking of solid residues directly. From a careful consideration of the whole subject, I am convinced that one of the most necessary steps to be taken in milk analysis is to abandon the use of the lacto- meter. The creamometer is a graduated tube, in which milk is