234 SOFTENING WATER FOR SPRAYS 



washing-soda and soap to efifect the same purpose 

 render softening by the former very economical. 



224. Examination of Soft Soap. 



The examination of soft soap for making up washes, etc., is 

 generally limited to a determination of the lathering power and the 

 amount of carbonate present. The latter increases in quantity 

 with the age of the soap, which should not be kept too long. 



id) Lathering Power. — It is best to compare the 

 material with first-class soap of which the lathering 

 power with the water of the district is known. Ten 

 grams of the soft soap are dissolved in dilute alcohol 

 and the solution made up to i litre. The amount 

 required to produce a lather with 50 c.c. of tap-water is 

 determined as in 222 {a), p. 230. The amount of soap 

 in pounds required to give a lather with 100 gallons 

 of the water is then calculated. Each part of soap 

 required per 100 parts of water = one-tenth pound 

 per gallon. 



With a water of 20 degrees of hardness a good soft soap will 

 require, to produce a lather, 3-5-4 lbs, per 100 gallons, 



{U) Carbonate. — Twenty grams of the soap are dried 



in the steam-oven, the residue weighed and then 



dissolved by warming with 200 c.c. of absolute alcohol. 



The liquid is filtered, the undissolved residue, if any, 



dissolved in hot water, and the solution thus obtained 



N 

 titrated with — sulphuric acid, using methyl orange as 



indicator. The alkali determined in this way is calcu- 

 lated as KnCOo. 



