Alkalinity : Mix g with 5 ml of ethanol (96 per cent) and ml of phenol red solution. Add 50 ml of carbon dioxide-free water and examine immediately. No reddish colour appears.
Alkali and alkaline-earth metals : Maximum per cent.
To g add 25 ml of water and 5 ml of hydrochloric acid and heat to boiling. Filter whilst hot. Wash the filter and the residue with 25 ml of hot water. Combine the filtrate and washings and add concentrated ammonia until alkaline. Add ml of thioacetamide solution and heat on a water-bath for 30 min. Filter and wash the precipitate with 2 quantities, each of 10 ml, of water. Combine the filtrate and washings, evaporate to dryness on a water-bath and ignite. The residue weighs a maximum of 20 mg.
Sulphates : Maximum 500 ppm.
Loss on drying : Maximum per cent, determined on g by drying in an oven at 105C.
Degree of un-saturation : Dissolve g in a mixture of 5 ml of dilute hydrochloric acid R and 30 ml of glacial acetic acid. Using ml indigo carmine solution, added towards the end of the titration as indicator. Titrate with M bromide-bromate until the colour changes from blue to yellow.
ml to ml of M bromide-bromate is required. Carry out a blank titration.