The Phosphates of Milk. 
159 
and, although always found in the ash of curd in pretty constant pro- 
portion, do not enter into its proper composition at all. M. Duclaux 
lias made new determinations of the matters which milk holds in 
suspension as distinct from solution, by exact analyses of the entire 
milk, and of the clear portion which passes through a Chamberland 
biscuit-filter. This filtration must he conducted with precautions, 
since even when pressure is employed it takes twenty-four hours to 
pass 100 cubic centimetres 1 of milk through such a filter, and during 
this time acidity develops and increases under ordinary circumstances, 
and so more and more phosphate of lime passes into solution. To 
prevent this the milk is either sterilised before filtration, or is cooled 
by ice ; the filter itself and the receiving vessel are carefully steri- 
lised previous to use by being passed through a flame. 
The ingredients of milk in suspension consist of the fat, seven- 
eighths of the casein, and nearly half of the minerals. The present 
paper is restricted to an investigation of the minerals only, with 
especial regard to the state of combination of the phosphates. 
The analytical methods adopted by Duclaux for the determination 
of the proximate ingredients of the ash are detailed in the paper, 
but need not be repeated here. The results only, which are of 
considerable interest, need be quoted. 
Composition op the Asii of 100 Cubic Centimetres 1 of Milk. 
Alumina and oxide of iron 
Magnesia 
Lime .... 
Phosphoric acid 
Not estimated , . 
Minerals in 
Entire milk. 
Grammes 
Filtered'milk. 
Grammes 
suspension 
(difference). 
Grammes 
, 0-005 
0-002 
0003 
0017 
0-011 
0-006 
0-178 
0-051 
0-127 
, 0-213 
0-088 
0-125 
, 0-339 
0-302 
0-037 
0752 0-454 0-298 
The nature of the phosphates in suspension is hardly open to 
doubt ; they may be arranged thus : — 
Phosphates of iron and alumina . 
Phosphate of magnesia (tribasic) 
» 
lime 
Grammes 
0-006 
0013 
0-235 
0-254 
When the ingredients are combined thus, there is still an excess 
of 0-007 grammes only of phosphoric acid not combined with lime, 
magnesia, or oxide of iron. This slight excess doubtless represents 
1 A hundred cubic centimetres (about i pint) is the quantity actually used 
by Duclaux for the filtration. The results may be read in English standards 
as grains of the various ingredients found in 100 grain-measures of milk, or, 
as milk is slightly heavier than water, grains per 103 grains of milk. They 
arc thus practically, but not exactly, equivalent to jicrcentaffes. 
