Dissolve the ash in distilled water and titrate total alkalinity, using as indicator methyl orange cold or litmus boiling.
3. _Determination of Alkali Present as Carbonate._--Take 10 grams of the sample, dilute with 50 cc. distilled water, add sufficient _N_/1 acid to neutralize the total alkali found at (2), boil under a reflux condenser for 15 to 20 minutes, wash down the condenser tube with distilled water, free from carbon dioxide, and then titrate back with _N_/1 NaOH, using phenolphthalein as indicator. Calculate the percentage of Na_{ 2}O. Deduct the Na_{ 2}O found in (1). The difference is the percentage of Na_{ 2}O existing as carbonate.
4. _Alkali Combined with Organic Acids._--The sum of the percentages of Na_{ 2}O found at (1) and (3) deducted from the percentage found at (2) is a measure of the Na_{ 2}O or other alkali combined with organic acids.
5. _Determination of Acidity._--Take 10 grams of the sample, dilute with 50 cc. distilled water free from carbon dioxide, and titrate with _N_/1 NaOH and phenolphthalein. Express in terms of Na_{ 2}O required to neutralize 100 grams.
6. _Determination of Total Residue at 160° C._--For this determination the crude glycerine should be slightly alkaline with Na_{ 2}CO_{ 3} not exceeding 0.2 per cent. Na_{ 2}O, in order to prevent loss of organic acids. To avoid the formation of polyglycerols this alkalinity must not be exceeded.
Ten grams of the sample are put into a 100 cc. flask, diluted with water and the calculated quantity of _N_/1 HCl or Na_{ 2}CO_{ 3} added to give the required degree of alkalinity. The flask is filled to 100 cc., the contents mixed, and 10 cc. measured into a weighed Petrie or similar dish 2.5 in. in diameter and 0.5 in. deep, which should have a flat bottom. In the case of crude glycerine abnormally high in organic residue a smaller amount should be taken, so that the weight of the organic residue does not materially exceed 30 to 40 milligrams.
The dish is placed on a water bath (the top of the 160° oven acts equally well) until most of the water has evaporated. From this point the evaporation is effected in the oven. Satisfactory results are obtained in an oven[20] measuring 12 ins. cube, having an iron plate 0.75 in. thick lying on the bottom to distribute the heat. Strips of asbestos millboard are placed on a shelf half way up the oven. On these strips the dish containing the glycerine is placed.