The laboratory book of dairy analysis / By H. Droop Richmond.

  • Richmond, Henry Droop
Date:
1905
Catalogue details

Licence: In copyright

Credit: The laboratory book of dairy analysis / By H. Droop Richmond. Source: Wellcome Collection.

Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.

    27/112 (page 15)
    (see Appendix) till a red colour just appears. Each cubic centimetre of silver solution indicates 0.00355 gramme of chlorine. \_Note.—A little of the chlorine, about 0.01 per cent., is lost on ignition of the total solids.]_ For the estimation of lime and phosphoric acid, it is advisable to take another quantity of milk (loc.c. or 25C.C. being preferable) ; this is dried on the water- bath, ignited, the ash dissolved in a little hydrochloric acid, and the solution boiled ; after cooling slightly, ammonia is added drop by drop till a permanent turbidity appears, and just sufficient hydrochloric acid added to remove this. The solution is just brought to the boiling-point, and a saturated solution of ammonium oxalate added drop by drop, so long as a precipitate appears; the solution is kept hot (in a water-oven) for at least two hours, and filtered through a small ash-free filter; the precipitate is transferred to the filter, washed with hot water, and the filter placed in a tared basin, and ignited over a small flame ; when the filter paper is all burnt away, the precipitate is moistened with a solution of ammonium carbonate, dried, and very gently ignited. The precipitate, now converted into calcium carbonate, is weighed, and the weight of lime found by multiplying by 0.56; it is usually slightly grey, and contains traces of iron, which are small enough to be neglected. To the filtrate is added 5 or loc.c. of magnesia mixture (see Appendix), and about one-tenth its volume of strong ammonia; and after stirring well the liquid is allowed to stand at least 12 hours; it is then filtered through an ash-free filter, the precipitate washed with dilute ammonia, and transferred to the filter, and well washed; the filter is placed in a weighed basin, and ignited at first gently, and finally very strongly till white; the residue of magnesium pyrophosphate is weighed, and the amount of phosphoric acid (as PgOg) found by multiplying by 0.6396. For the determination of other mineral constituents, works on mineral analysis shppl^ be consulted.