Total fatty matter
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Total fatty matter (TFM) is one of the most important characteristics describing the quality of soap and it is always specified in commercial transactions. It is defined as the total amount of fatty matter, mostly fatty acids, that can be separated from a sample after splitting with mineral acid, usually hydrochloric acid. The fatty acids most commonly present in soap are oleic, stearic and palmitic acids and pure, dry, sodium oleate has TFM 92.8%, while top quality soap noodles now increasingly used for making soap tablets in small and medium size factories, are typically traded with a specification TFM 78% min., moisture 14% max. But besides moisture, finished commercial soap, especially laundry soap, also contains fillers used to lower its cost or confer special properties, plus emollients, preservatives, etc. and then the TFM can be as low as 50%. Fillers, which are usually dry powders, also make the soap harder, harsher on the skin and with greater tendency to become 'mushy' in water and so low TFM is usually associated with hardness and lower quality. In older days in Europe and in some countries now, soap with TFM 75% minimum was referred to as Grade 1 and 65% minimum as Grade 2 and less 60% as Grade 3.
TFM should be 70% to 80% is referred is Grade 1 soaps.
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