The Dipping of Sheep in so-called Carbolic Dips. 541 



''A," some of the water was placed in a cliamber from which all air 

 was pumped. This had the effect of extracting from the water a good 

 proportion of its dissolved gases, including carbon-dioxide. The water 

 was then used to make an emulsion with *' A." The result was a 

 separation of 9.7 per cent, of oils, viz., 1.2 per cent, less than occurred 

 when the untreated fountain water was added to " A." It would, 

 therefore, seem that one must not overlook the presence in them of 

 free carbon-dioxide when judging of the suitability of a water for 

 mixing with a '^ carbolic " dip. 



The effect of removing both carbon-dioxide and calcium and 

 magnesium carbonates was studied in the following* way: — A water 

 of the kind we are dealing with loses its free carbon-dioxide and 

 deposits neorly all of its magnesium and calcium carbonates on being 

 boiled. A quantity of water was, therefore, boiled until its original 

 bulk was reduced to about one-half. The carbonates which separated 

 out were then removed by filtration, and the original volume of the 

 water restored by the addition of carbon-dioxide-free distilled water. 

 The water was then cooled to room temperature, after which an 

 appropriate quantity of " A " was mixed with it. The result was 

 that only 4.7 per cent, of the oils separated. 



Yet another experiment was made. 



Every one knows that when soap is added to hard water, as in 

 washing, a curdy precipitate is formed, and that the harder the water 

 the more soap one requires to produce a lather. The calcium and 

 magnesium salts of waters are those responsible for the formation of 

 the curdy precipitate, and it is not until the maximum amount of 

 curdy precipitate has been formed that the water will yield a per- 

 manent lather. Further, the curdy precipitate contains the calcium 

 and magnesium that were responsible for the hardness of the water. 

 In other words, soap softens water by removing calcium and 

 magnesium salts from it as a curdy precipitate. 



A quantity of water was, therefore, taken, and to it rather more 

 than enough soap solution was added to produce a permanent lather 

 on shaking. The curdy precipitate formed was separated by filtra- 

 tion, after which the water had added to it an appropriate quantity 

 of " A." Only 3.4 per cent, of oils separated out; another proof that 

 the destruction of the soap of the dip is very largely responsible for 

 the failure of it to form a true emulsion. It should, however, be 

 observed that although there was in this experiment an excess of soap 

 there was still an appreciable separation of oils ; tliis means that the 

 separation of the oils is not due to hardness of water alone. 



The results of the experiments are now summarized: — 



(1) It was not found possible to obtain a true emulsion by 



mixing " A " with either fountain or distilled water; but 

 distilled water mixtures contained very much less separated 

 oils than the fountain water mixtures. 



(2) The most perfect emulsion was obtained by boiling the dis- 



tilled water before mixing it with "A," the explanation 

 being that boiling expelled dissolved carbon-dioxide from 

 the water. 



(3) A slightly improved emulsion was obtained with fountain 



water by placing it in a vacuum cliamber (to remove 

 carbon-dioxide) before mixing it with " A." 

 19 



