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BRITISH PHARMACOPŒIA.


  British weights and measures.   Metric weights and measures.
   
  Grains weight of Substance. = Grain measures of Vol. Sol. or Grams, wt. of Substance. = C. C. of Vol. Sol.
Ferri Arsenias 100.0 = 225.0 or 10.00 = 22.50
Ferri Carb. Sacch 30.0 = 287.5 or 3.00 = 28.75
Ferri Phosphas 30.0 = 279.0 or 3.00 = 27.90
Ferri Sulphas 42.1 = 500.0 or 4.21 = 50.00
Ferri Sulphas Exsiccata 10.0 = 191.0 or 1..00 = 19.10
Ferri Sulphas Granulata 41.7 = 500.0 or 4.17 = 50.00

VOLUMETRIC SOLUTION OF HYPOSULPHITE OF SODIUM.

(Hyposulphite of Sodium crystallised, = 248.)

Take of

Hyposulphite of Sodium, in crystals 280 grains
Distilled Water a sufficiency

Dissolve the hyposulphite of sodium in 10,000 grain-measures of water. Fill a burette with this solution, and drop it cautiously into 1,000 grain-measures of the volumetric solution of iodine, until the brown colour is just discharged. Note the number of grain-measures (n) required to produce this effect; then put 8,000 grain-measures of the same solution into a graduated jar, and augment this quantity by the addition of distilled water until it amounts to gram-measures. If, for example, n=950, the 8,000 grain-measures of solution should be diluted to the bulk of =8,421 grain-measures. 1,000 grain-measures of this solution contain 24.8 grains of the hyposulphite (1/10th of , in grains), and therefore correspond to 12.7 grains of iodine (1/10 th of an atomic weight in grains).

Grammes and cubic centimetres may be employed instead of grains and grain-measures, but for convenience 1/10 th of the numbers should be taken. 100 cubic centimetres of this solution contain 2.48 grammes of the hyposulphite (1/100 th of ,, in grammes), and therefore correspond to 1.27 gramme of iodine (1/100th of an atomic weight in grammes).

This solution is used for testing the following substances.