About 2 grammes of the sample are dissolved in 50 c.c. distilled water, and titrated with N/1 sulphuric acid, using phenol-phthalein as indicator, the alkalinity so obtained representing all the caustic alkali and one-half the carbonate, which latter is converted into bicarbonate. One c.c. N/1 acid = 0.031 gramme Na_{2}O or 0.040 gramme NaOH and 0.047 gramme K_{2}O, or 0.056 gramme KOH. After this first titration, the second half of the carbonate may be determined in one of two ways, either:-- (1) By adding from 3-5 c.c. of N/10 acid, and well boiling for five minutes to expel carbonic-acid gas, after which the excess of acid is titrated with N/10 soda solution; or (2) After adding two drops of methyl orange solution, N/10 acid is run in until the solution acquires a faint pink tint. In the calculation of the caustic alkali, the number of c.c. of acid required in the second titration, divided by 10, is subtracted from that used in the first, and this difference multiplied by 0.031, or 0.047 gives the amount of Na_{2}O or K_{2}O respectively in the weight of sample taken, whence the percentage may be readily calculated. The proportion of carbonate is calculated by multiplying the amount of N/10 acid required in the second titration by 2, and then by either 0.0031 or 0.0047 to give the amount of carbonate present, expressed as Na_{2}O or K_{2}O respectively. An alternative method is to determine the alkalinity before and after the elimination of carbonate by chloride of barium. About 7-8 grammes of the sample are dissolved in water, and made up to 100 c.c., and the total alkalinity determined by titrating 20 c.c. with N/1 acid, using methyl orange as indicator. To another 20 c.c. is added barium chloride solution (10 per cent.) until it ceases to give a precipitate, the precipitate allowed to settle, and the clear supernatant liquid decanted off, the precipitate transferred to a filter paper and well washed, and the filtrate titrated with N/1 acid, using phenol-phthalein as indicator. The second titration gives the amount of caustic alkali present, and the difference between the two the proportion of carbonate. When methyl orange solution is used as indicator, titrations must be carried out cold. Reference has already been made (p. 39) to the manner in which the alkali percentage is expressed in English degrees in the case of caustic soda. _Chlorides_ are estimated by titrating the neutral solution with N/10 silver nitrate solution, potassium chromate being used as indicator. One c.c. N/10 AgNO_{3} solution = 0.00585 gramme sodium chloride. The amount of acid necessary for exact neutralisation having already been ascertained, it is recommended to use the equivalent quantity of N/10 nitric acid to produce the neutral solution. _Sulphides_ may be tested for, qualitatively, with lead acetate solution.