Third--About 5 grams of soap are weighed and dissolved in 100 cubic centimeters of 50 per cent. neutralized alcohol in a 250 cubic centimeter Erlenmeyer flask over a water bath and connected with a reflux condensor. When completely dissolved, which takes but a few moments, it is cooled by allowing a stream of running water to run over the outside of the flask. Fourth--The soap is precipitated with 15 to 20 cubic centimeters of the 10 per cent. barium chloride solution. Fifth--After the addition of 2 to 5 cubic centimeters of [Greek: alpha] naphtholphthalein solution the solution is titrated with N/40 alcoholic stearic acid. [Greek: alpha] naphtholphthalein is red with an excess of stearic acid. To mark the color changes it is advisable to first run a few blanks until the eye has become accustomed to the change in the indicator in the same way. The change from green to red can then be carefully observed. Let us presume 5 grams of soap were taken for the analysis and 20 cubic centimeters of N/40 stearic acid were required for the titration then to calculate the amount of NaOH since the stearic factor is 1.016. 20 x 1.016 = 20.32 N/40 stearic acid really required. 1 cubic centimeter N/40 stearic acid = 0.02 per cent. NaOH for 5 grams soap. [Greek: Delta] 20.32 cubic centimeters N/40 stearic acid = 0.02 x 20.32 per cent. NaOH for 5 grams soap. Hence the soap contains 0.4064 per cent. NaOH. It is necessary, however, to make a correction by this method. When the free alkali amounts to over 0.1 per cent. the correction is + 0.01, and when the free alkali exceeds 0.4 per cent. the correction is + 0.04, hence in the above case we multiply 0.004064 by 0.04, add this amount to 0.004064 and multiply by 100 to obtain the true percentage. Should the alkalinity have been near 0.1 per cent. we would have multiplied by 0.01 and added this. If carbonate is also present in the soap, another 5 grams of soap is dissolved in 100 cubic centimeters of 50 per cent. alcohol and the solution titrated directly after cooling with N/40 stearic acid, using [Greek: alpha] naphtholphthalein or phenolphthalein as an indicator, without the addition of barium chloride. From the difference of the two titrations the alkali present as carbonate is determined. If the decomposed soap solution is colorless with phenolphthalein, free fatty acids are present, which may be quickly determined with alcoholic N/10 sodium hydroxide. INSOLUBLE MATTER. The insoluble matter in soap may consist of organic or inorganic substances. Among the organic substances which are usually present in soap are oat meal, bran, sawdust, etc., while among the common inorganic or mineral compounds are pumice, silex, clay, talc, zinc oxide, infusorial earth, sand or other material used as fillers.