When the rules laid down by Dakin and by Daufresne for the manufacture of hypochlorite of soda are followed, the solution fulfils all the desired conditions. Experience has shown us, however, that in the various hospitals where Dakin's solution is said to have been in use, they often employ under this name various mixtures, more or less dangerous. These defective solutions, which do irritate tissues and do not sterilise wounds, are the result of more or less clumsy faults in technique.

1st. The worst error consists in attributing to eau de Javel or Labarraque's liquor mixed with a certain proportion of boric acid, the properties possessed by Dakin's solution. A certain number of surgeons are not afraid to use similar solutions. Thus in one large hospital a mixture of Labarraque's liquor and 40 per cent. boric solution was employed under the name of "Dakin's Solution." It is perfectly certain that solutions of which one does not know the content, either of the alkali or the hypochlorite of soda, are useless or dangerous.

2nd. Other errors crop up when hypochlorite of soda solution is prepared according to Dakin's method, but by means of chloride of lime of which the content of active chlorine is not known. The result is that the proportions of carbonate and bicarbonate of soda are no longer exact, and the product obtained is no longer Dakin's solution. Therefore it is indispensable to verify always the titration of chloride of lime; and, the solution once obtained, to titrate the quantity of hypochlorite which it contains and to apply the phtalein test according to Dakin's technique. Hence, errors in the mode of preparation result in solutions which are irritating because they contain too much alkali or too much hypochlorite of soda; or which fail to sterilise wounds because the amount of hypochlorite of soda is too small, or which do not keep well because they are charged with too much boric acid.

3rd. Mistakes may be made in the way in which the solution is kept. Should hypochlorite of soda be kept in small quantities exposed to light and heat, the strength of the solution rapidly lessens. We have seen in use in a hospital, a solution whose hypochlorite content had diminished to nearly 0.05. These mistakes are readily avoided by using fresh solutions, or rather by taking pains to keep the solution in darkness and in a cool place. It is prudent to make titrations of the hypochlorite of soda from time to time.

4th. Errors in the strength of the solution also occur. In certain hospitals we have seen a solution used whose hypochlorite content was correct, but whose strength was reduced by addition of water. Solutions thus obtained have a bactericidal potency far too feeble, and they must not be used. Since, as the result of numerous experiments, it has been determined that a solution varying from 0.45 to 0.50 per cent. has no irritating action on the tissues when used under the conditions previously described, Dakin's solution pure and simple should be employed. There is no danger when it is accurately prepared. It is important to make sure that the details of the method previously described have been followed to the letter, if it is desired to obtain Dakin's solution with its characteristic properties. Furthermore, the procedure for sterilisation has been calculated with a view to the application of a liquid possessing the strength and qualities of Dakin's solution, so that any alteration in the solution robs the method of its precision and its efficacy.