NATURE OF DEPOSIT OBTAINED FROM MILK. 163 
indications that there may be another substance of higher 
ash-content yet which comes down after this. The data 
are as yet, however, not sufficient to admit of any definite 
inference being drawn from them. 
4. Amount of Calcium and Phosphorus in the Deposit. 
Methods of Analysis.—The dried deposits: were ashed in 
a muffle as described, the ash was dissolved in dilute hydro- 
chloric acid, and the CaO was estimated in this solution. 
The P.O; was estimated in the filtrate and washings from 
the CaO estimation. The method used for the estimation 
of calcium was that developed by McCrudden (1911) for 
dealing with organic ashes, in which calcium, magnesium, 
iron, and phosphorus are present together. In the case of 
a small quantity of calcium such as we are dealing with 
here, the procedure is as follows:—The acid solution of the 
ash is diluted to 100 cc., made just alkaline with ammonia 
(a precipitate of calcium phosphate forms), then made just 
acid again with hydrochloric acid (the precipitate redis- 
solves),and ten drops more of concentrated hydrochloricacid 
are added. Ten cc. of a 2°5% solution of oxalic acid are 
then added, and finally 8 cc. of a 20% solution of sodium 
acetate. The solution is either allowed to stand over night 
before filtering, or shaken vigorously in a stoppered vessel 
for ten minutes. The precipitate is then washed free from 
chloride in the usual way, and ignited to CaO, in which 
form it is weighed. In the present case the precipitates 
were ignited by placing them with the filters while still 
wet in the crucibles and introducing directly into a glowing 
muffle. The water in the crucible almost at once assumes 
the spheroidal condition, and the drying and ignition proceed 
quietly; there is no spluttering nor danger of breaking the 
porcelain crucible. 
P.O, was determined in the filtrate and washings from 
the above estimation. These were made just alkaline with 
