Reports of the special Committee upon Pathological Methods. V, The reaction of media.

  • Great Britain. Medical Research Committee. Special Committee upon Pathological Methods.
Date:
1919
Catalogue details

Licence: Public Domain Mark

Credit: Reports of the special Committee upon Pathological Methods. V, The reaction of media. Source: Wellcome Collection.

    13/20 page 11
    ME The apparatus necessary for preparing the standard tubes of definite hydrogen ion concentration are : 1. Standard burette, 50 c.c. in 1/10ths. 2. Standard 100 c.c. flasks. 3. Tubes to contain the standard solutions, These are made from ‘cordite’ tubes. They are thoroughly cleaned by boiling with distilled water, rinsed out several times with water, and dried in the water oven. They are then drawn out in the blow-pipe flame about 8 cm. from the sealed end so that a constriction is formed about 3 mm, in diameter through which they can subsequently be filled. 4, Small capillary funnel made from a test-tube by drawing out a neck less than 3mm. in diameter and about 15 cm. long. The method of making the mixtures is as follows: The volume of the disodium phosphate solution is measured into a carefully cleaned 100 c.c. graduated flask from the burette, and the volume made up exactly to 100 cc. with the acid potassium phosphate. The mixture so obtained will have the corresponding hydrogen exponent. The ‘cordite’ tubes are then filled with this solution, using the small capillary funnel. It is advisable to place a few small crystals of thymol in the tubes to prevent any bacterial growth. The tubes are numbered and the proper Py indicated upon them, and are sealed in the blow-pipe and are ready for use. ‘They should be kept in the dark when not in use. | As the dihydrate of sodium phosphate is somewhat difficult to prepare, and the dihydrogen potassium phosphate crystallizes with ease, an alternative method is given for preparing solutions of definite hydrogen ion concentration from the latter salt. ' The solutions necessary are: 1. A 1/5 normal solution of dihydrogen potassium phosphate containing phenol red. This is made by weighing out 13°616 grams of that salt. This is dissolved in about 300 c.c. of boiled distilled water. ‘To the solution is added 90-6 c.c. of a 0-02 per cent. solution of phenol red. The mixture is then made up to 500 c.c. 2. A N/10 solution of sodium hydroxide. From these two solutions the following mixtures are made up: N/s5 KH,PO, N/to NaOH Water to Pr 25 17°o 100 6°6 pa 23°05 100 6:8 25 29°63 100 7°0 25 35°00 100 792 25 39°59 - 100 7*4 25 42°80 100 7°6 25 45°20 100 7S 25 40°So 100 8°O 1 ‘ Cordite tubes’ are specially selected tubes of hard white glass which have a uniform thickness of wall and external diameter. They are used in certain colour reactions in the routine testing of cordite. Test-tubes of good quality may also be used, provided that a careful selection is made, so that they are all of the same measurements. The cordite tubes may be obtained from Baird and Tatlock, Cross Street, Hatton Garden, London, E.C,
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