41 A DARIN'S SOLUTION 



litres of tap-water; shake vigorously two or three times and 

 leave it all night. 



Dissolve the carbonate and bicarbonate of soda in 5 

 litres of cold water. 



Pour the solution of soda salts into the flask containing 

 the suspended chloride of lime, shake well during one min- 

 ute, and set aside to allow the lime carbonate to settle. 



At the end of half an hour siphon off the clear liquid and 

 filter it through a double paper to make it perfectly clear. 



The antiseptic solution is then ready for- surgical use. 

 It should contain 0.475 per cent, of hypochlorite of soda, 

 with small quantities of neutral salts of soda. It is iso- 

 tonic to blood serum. 



Keep the solution in a cool place, away from light. 



If the chloride of lime used contains materially more or 

 less active chlorine than 25 per cent., it is important to 

 alter the proportion of the three substances used in the 

 preparation of the solution. For this reason the amount of 

 active chlorine in the sample should be tested as follows : 



Weigh out an average sample of 20 grams, stir it up in a 

 litre of water as perfectly as possible, and allow it to stand 

 some hours. Measure off 10 c.c. of the clear liquid, add to 

 it 20 c.c. of a 10 per cent, solution of iodide, 2 c.c. of acetic 

 acid or hydrochloric acid, then to the mixture add drop by 

 drop a decinormal solution of hyposulphite of soda (2.48 

 per cent.), up to decolorization. The number (n) of cubic 

 centimeters of hyposulphite employed multiplied by 1775 

 will give the weight (N) of active chlorine contained in 100 

 grams of the chloride of lime. 



This estimation must be carried out for each consign- 

 ment received. Should the result obtained differ from the 



