Volumetric Solution of Hyposulphite of Soda (hyposulphite of soda crystallised, NaO1S2O2 + 5HO = 124, or Na2H2S2O4.4H20 = 248).
| Take of— | |
| Hyposulphite of soda, in crystals | 280 grains. |
| Distilled water | a sufficiency. |
Dissolve the hyposulphite of soda in 10,000 grain-measures of water. Fill a burette with this solution and drop it cautiously in 1000 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 8000 grain-measures of the same solution into a graduated jar, and augment this quantity by the addition of distilled water until it amounts to (8000 × 1000) / n grain-measures. If, for example, n = 950, the 8000 grain-measures of solution should be diluted to the bulk of (8000 × 1000) / 950 = 8·421 grain-measures. 1000 grain-measures of this solution contains 24·8 grains of the hyposulphite (1⁄10th of 2(NaO,S2O2 + 5HO), or 1⁄10th of Na2H2S2O4,4H2O in grains), and therefore corresponds to 12·7 grains of iodine (1⁄10th of an equivalent).
Grammes and cubic centimètres may be employed instead of grains and grain-measures, but for convenience 1⁄10th of the numbers should be taken. 100 cubic centimètres of this solution contain 2·48 grammes of the hyposulphite (1⁄100 of 2(NaO,S2O2+ 5HO), or 1⁄100th of Na2H2S2O4.4H2O in grammes), and therefore corresponds to 1·27 grains of iodine (1⁄100th of an equivalent).
This solution is used for testing the following substances. In each case, except that of iodine, a solution of iodide of potassium and hydrochloric acid are added to the substance, and the amount of iodine so liberated is indicated by this solution:
| British Weights and Measures. | or | Metrical Weights and Measures. | |||||
| Grains weight of substance. | = | Grain-measures of vol. sol. | Grams weight of substance. | = | C. C. of vol. sol. | ||
| Calx Chlorata | 10·0 | = | 850 | or | 1·00 | = | 85·0 |
| Iodum | 12·7 | = | 1000 | ” | 1·27 | = | 100·0 |
| Liq. calc. chloratæ | 60·0 | = | 500 | ” | 6·00 | = | 50·0 |
| Liq. chlori | 439·0 | = | 750 | ” | 43·90 | = | 75·0 |
| Liq. Sodæ chloratæ | 70·0 | = | 500 | ” | 7·00 | = | 50·0 |
Volumetric Solution of Iodine (iodine, I = 127, or I = 127).
| Take of iodine | 127 | grains. |
| Iodide of potassium | 180 | ” |
| Distilled water | a | sufficiency. |
Put the iodide of potassium and the iodine into the 10,000 grain flask, fill the flask to about two thirds its bulk with distilled water, gently agitate until solution is complete, and then dilute the solution with more water, until it has the exact volume of 10,000 grain-measures. 1000 grain-measures of this solution contain 1⁄10th of an equivalent in grains (12·7 grains) of iodine, and therefore correspond to 1·7 grains of sulphuretted hydrogen, 3·2 grains of sulphurous acid, and 4·95 grains of arsenious acid.
Grammes and cubic centimètres may be employed instead of grains and grain-measures, but for convenience 1⁄10th of the numbers should be taken. 100 cubic centimètres contain 1·27 grammes of iodine, and correspond to 0·17 grammes of sulphuretted hydrogen, 0·32 grammes of sulphurous, and 0·495 grammes of arsenious acid. This solution is for testing the following substances. It is dropped from the burette into the liquid to be tested, until free iodine begins to appear in the solution.