Bacteriological techniques for dairy purposes.

  • Great Britain. Ministry of Agriculture, Fisheries and Food.
Date:
1968
Catalogue details

Licence: Public Domain Mark

Credit: Bacteriological techniques for dairy purposes. Source: Wellcome Collection.

    188/192 (page 180)
    PREPARATION OF REAGENTS All solutions must be prepared using distilled water or water of equivalent purity. Disodium Dthydrogen Ethylenediaminetetra-Acetate, (EDTA), N/50. Dissolve 3-72g crystalline dihydrate in water and dilute to 1 litre. Check against standard hard water. (1 ml N/50 EDTA=1 ml standard hard water). Ammonium Buffer. Add 67:5g ammonium chloride to 570 ml ammonia, sp. gr. 0°880, and dilute to 950 ml with water. Dissolve 0-616g magnesium sulphate, MgSO,. 7H,O, in 50 ml water and add 0-93g solid EDTA reagent. When this is in solution add it to the ammonia and ammonium chloride mixture. The addition of 2 ml buffer in 100 ml of water is equivalent to the addition of 5 p/m magnesium in terms of CaCO, together with its equivalent of EDTA. Total Hardness Indicator. Add 0:5g Solochrome Black WDFA or Erio- chrome Black T to 100 ml industrial methylated spirit, warm to dissolve the dyestuff and add 4-5g hydroxylamine hydrochloride. Allow to stand overnight and filter. This indicator will not keep for more than 1 month. Standard Hard Water. Dissolve 1g calcium carbonate in 20 ml N hydro- chloric acid and dilute to 1 litre. 1 ml=1 mg CaCOs. Screened Indicator. Weigh out 0-06g brom-cresol green and 0-04g methyl red and dissolve in 100 ml industrial spirit (85 per cent ethanol).