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:-- 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:--