Take from different parts of the bar a small quantity of beaching powder to have a medium sample, weigh 20 grammes of it, mix as well as possible in a litre of tap water and leave in contact for a few hours. Measure 10 c.c. of the clear liquid and add 20 c.c. of a 10% solution of potassium iodide, 2 c.c. of acetic acid or hydrochloric acid, then put drop by drop into the mixture a decinormal solution of sodium hyposulfite (2.48%) until decoloration. The number "N" of cubic centimeters of hyposulfite employed multiplied by 1,775 will give the weight "N" of active chloride contained in 100 grammes of chloride of lime.
The test must be made every time a new product is received. When the result obtained will differ more or less than 25%, it will be necessary to reduce or enlarge the proportion of the three products contained in the preparation. This can be easily obtained by multiplying each of the three numbers—200, 100, 60 by the factor N/25 in which N represents the weight of the active chlorine per cent of chloride of lime.
Measure 10 c.c. of the solution, add 20 c.c. of potassium iodide 1/10, 2 c.c. of acetic acid and drop by drop a decinormal solution of sodium hyposulfite until decoloration. The number of cubic centimeters used multiplied by 0.03725 will give the weight of the hypochlorite of soda contained in 100 c.c. of the solution.
Never heat the solution and if in case of urgency one is obliged to resort to trituration of chloride of lime in a mortar, only employ water, never salt solution.
Test of Thetalkalinity of Dakin Solution:—
To easily differentiate the solution obtained by this process from the commercial hypochlorites, pour into a glass about 20 c.c. of the solution and drop on the surface of the liquid a few centigrammes of phenol-phthaleine in powder. The correct solution does not give any coloration while Lebarraque's solution and Rau de Javel will give an intense red color which shows in the last two solutions existence of free caustic alkali.
TECHNIQUE—Dakin Solution.
The procedure is very simple. The solution, however, must be between 45 to 50% hypochlorite. Anything above this strength will burn and anything below is too weak. The edges of the wound should be covered with gauze which has been well soaked in vaseline, the solution should then be introduced into the wounds from an irrigator every two hours. A stopcock should be put on the tube and only sufficient solution should be allowed to enter the wound to completely saturate all parts of the wound. In other words, the wounds should be bathed with the solution every two hours—do not mistake this and irrigate continuously. You can easily tell how much solution it takes to keep the wound wet.
Rubber tubes are used. The end of the tube is tied off and six to eight small perforations are made so that the solution can run into all parts of the wound. If the wounds are superficial, the same kind of a tube can be used to which a cuff of turkish towel is wrapped around the end of the tube.
If you feel that the wounds are sure to be infected, it would be well to lay them open freely and immediately start this treatment, be sure to have the skin well protected with the vaseline and gauze and see that the solution does not run out of the wound on the bed. Just keep the wound bathed every two hours.