The potassium platino-chloride (K_{2}PtCl_{6}) is calculated to potassium chloride (KCl) by using the factor 0.3052, and this figure deducted from the amount of mixed chlorides found, gives the amount of sodium chloride (NaCl), from which the sodium oxide (Na_{2}O) is obtained by multiplying by 0.52991. The potassium chloride (KCl) is converted into terms of potassium oxide (K_{2}O) by the use of the factor 0.63087. _Salt_ may be determined in 50 c.c. of the filtered aqueous extract of the incinerated soap, by exactly neutralising with normal acid and titrating with N/10 silver nitrate solution, using a neutral solution of potassium chromate as indicator. The final reaction is more distinctly observed if a little bicarbonate of soda is added to the solution. Number of c.c. required x 0.00585 x 100 = per cent. of common salt, NaCl. Chlorides may also be estimated by Volhard's method, the aqueous extract being rendered slightly acid with nitric acid, a measured volume of N/10 silver nitrate solution added, and the excess titrated back with N/10 ammonium thiocyanate solution, using iron alum as indicator. _Silicates._--These are estimated by evaporating 50 c.c. of the filtered extract from the incinerated soap, in a platinum dish with hydrochloric acid twice to complete dryness, heating to 150 deg. C., adding hot water, and filtering through a tared filter paper. The residue is well washed, ignited, and weighed as SiO_{2}, and from this silica is calculated the sodium silicate. _Sulphates_ may be determined in the filtrate from the silica estimation by precipitation with barium chloride solution, and weighing the barium sulphate, after filtering, and burning, expressing the result in terms of Na_{2}SO_{4} by the use of the factor 0.6094. _Moisture._--This is simply estimated by taking a weighed portion in small shavings in a tared dish, and drying in the oven at 105 deg. C. until it ceases to lose weight. From the loss thus found is calculated the moisture percentage. _Free or Uncombined Fat._--This is usually determined by repeated extraction of an aqueous solution of the soap with petroleum ether; the ethereal solution, after washing with water to remove traces of soap, is evaporated to dryness and the residue weighed. A good method, which can be recommended for employment where many determinations have to be performed, is to dissolve 10 grammes of soap in 50 c.c. neutral alcohol and titrate to phenol-phthalein with N/1 acid. Add 3-5 drops HCl and boil to expel carbonic acid, neutralise with alcoholic KOH solution and add exactly 10 c.c. in excess, boil for fifteen minutes under a reflux condenser and titrate with N/1 acid. The difference between this latter figure and the amount required for a blank test with 10 c.c. alcoholic KOH, denotes the amount of alkali absorbed by the uncombined fat. _Examination of the fatty acids_ as a guide to the probable composition of the soap:--