CARREL-DAKIN SOLUTION 



373 



must be exactly between 0.45 and 0.50 per cent, in the finished 

 product. Chlorinated lime, sodium carbonate and sodium bicarbon- 

 ate are required for making the solution. Since the chlorinated lime 

 varies so greatly in its chlorine content, which is the active in- 

 gredient, it is necessary to determine the amount in each case. This 

 is done by thoroughly mixing 20 gms. of the chlorinated lime to be 

 used with one liter of ordinary water, allow to stand for a few 

 hours, with occasional agitation, then filter. Then take 10 mils of 

 the filtered solution, 20 mils of a 1 — 10 solution of potassium iodide 

 and 2 mils of acetic or hydrochloric acid and titrate dropwise with 

 a deci-normal sodium thiosulphate solution until decoloration is com- 

 plete. The amount of sodium thiosulphate solution used, in mils 

 multiplied by 1.T75 gives the weight of the active chlorine in 100 

 grams of the chlorinated lime. Then by referring to the accom- 

 panying table the amounts of the various agents required to make 

 10 liters of solution may be obtained. 



For instance, if the volume of the thiosulphate solution required 

 is 16.6 mils — 16.6 multiplied by 1.7Y5 equals 29. Y grams (29.7 per 

 cent.) chlorine in 100 grams of the chlorinated lime. This corre- 

 sponds very closely in the table to 



Chlorinated lime 154 gms. 



Dry Sodium Carbonate 77 gms. 



Sodium Bicarbonate 64 gms. 



Quantities of Ingredients foe Ten Liters of Dakest's Solution. 



Liter of Chlorinated Anhydrous Sodium 



Chlorinated Lime. Gm. Sodium Bicarbonate 



Lime Carbonate, Gm. Gm. 



20 230 115 96 



21 220 110 92 



22 210 105 88 



23 200 100 84 



24 192 96 80 



25 184 92 76 



26 177 89 72 



27 170 85 70 



28 164 82 68 



29 159 80 66 



30 154 77 64 



31 148 74 62 



32 144 72 60 



33 140 70 59 



34 135 68 57 



35 132 66 55 



36 128 64 53 



37 124 62 52 



To prepare 10 liters of solution, weigh the agents carefully, place 

 the chlorinated lime and 5 liters of ordinary water in a jar of 

 about 12 liters capacity, agitate well for a few minutes and allow 



