| 1— | To prepare 10 litres of solution, weight exactly: | |
| Chloride of Lime (Bleaching Powder) | 200 grms. | |
| Carbonate of Soda (dried) | 100 grms. | |
| or if used in crystals | 200 grms. | |
| Bi-carbonate of Soda | 200 grms. | |
| 2— | Put the Chloride of Lime into a large mouthed bottle of about 12litres capacity. Add 5 litres of water (half the quantity) andshake well two or three times. Let this stand all night. | |
| 3— | Dissolve in another 5 litres of water of two Soda salts. | |
| 4— | this latter solution directly into the bottle containingthe maceration of lime. Stir well and let the solution stand inorder to allow the precipitate of Carbonate of Lime to settle. | |
| 5— | At the end of half an hour, siphon the clear liquid and filterby means of a paper, in order to have a perfectly clear solution.This should be kept away from the light. | |
| 6— | No heat should be employed in the manufacture of Dakin's and ordinary Tapwater should be used. |
Preparation of Dakin Solution.
Technique of Dr. Daufresne.
The solution of sodium hypochlorite for surgical use must be free of caustic alkali; it must only contain 0.45% to 0.50 of hypochlorite. Under 0.45% it is not active enough and above 0.50 it is irritant. With chloride of lime (bleaching powder) having 25% of active chlorine, the quantities of necessary substances to prepare ten litres of solution are the following:—
| Chloride of Lime (bleaching powder) 25% CI act. | 200 gr. |
| Sodium Carbonate, dry (Soda of Solway) | 100 gr. |
| Sodium Bi-carbonate | 80 gr. |
Pour into 12 litre flask the two hundred grammes of chloride of lime and five litres of ordinary water, shake vigorously for a few minutes and leave in contact for six to twelve hours, one night for example. (Shake until dissolved) at least the big pieces are dissolved, large pieces float—notice only floating pieces. At the same time, dissolve in five litres of cold ordinary water the carbonate and bi-carbonate of soda.
After leaving from six to twelve hours, pour the salt solution in the flask containing the macerated chloride of lime, shake vigorously for a few minutes and leave to allow the calcium carbonate to be precipitated. In about half an hour, siphon the liquid and filter with a double paper to obtain a good, clear liquid, which should always be kept in a dark place.
Tritration of Chloride of Lime (Bleaching Powder).
Because of the variation of the products now obtained in the market, it is necessary to determine the quantity of active chlorine contained in the chloride of lime which is to be used. This, in order to employ an exact calculated quantity according to its concentration. The test is made in the following manner:—