Acidulants: analysis

Most manufacturers use soapstock to spray on meal for animal feed, or ship the material to acidulators. Some seed oil producers treat soapstock on site with sulfuric acid at a temperature of 90-95 °C to produce acidulated soapstock (Dijkstra and Segers, 2007). Acidulated soapstock is very dark in color with a strong, rancid, burned odor from the free fatty acids and neutral oils. Free fatty acid content varies and can be in excess of 90%. Moisture content as well as unsaponifiables can be substantial and the pH (based on samples provided to Stepan Company) may vary from 3 to 4.5. An example of a typical analysis of an acid oil sample is listed below (Table 6.2). 

The detection of elementary phosphorus in a systematic toxicological analysis is connected with that of prussic acid, alcohol, ether, chloroform, and other volatile poisons. The substances under examination are diluted with HjO, acidulated with HnSO<, and heated over a sand-bath in the flask a (Fig. 28). This flask is connected with a CO-i generator, 6, whose stopcock is closed. 

Notwithstanding the volatility and instability of the poison, its presence has been detected two months after death, although the chances of separating it are certainly the better the sooner after death the analysis is made. The search for hydrocyanic acid is combined with that for phosphorus the part of the distillate containing the more volatile products is examined by the tests given above. It is best, when the presence of free hydrocyanic acid is suspected, to distil at first without acidulating. In cases of suspected homicide by hydrocyanic acid the stomach should never be opened until immediately before the analysis. 

Analysis.—In fatal cases of poisoning by oxalic acid the contents of the stomach are sometimes strongly acid in reaction more usually, owing to the administration of antidotes, neutral, or even alkaline. In a systematic analysis the poison is to be sought for in the residue of the portion examined for prussic acid And phosphorus or, if the examination for those substances be omitted, in the residue or final alkaline fluid of the process for alkaloids. If oxalic acid alone is to be sought for, the contents of the stomach, or other substances if acid, are extracted with water, the liquid filtered, the filtrate evaporated, the residue extracted with alcohol, the alcoholic fluid evaporated, the residue redissolved in water (solution No. 1). The portion undissolved by alcohol is extracted with alcohol acidulated wdth hydrochloric. acid, the solution evaporated after filtration, the residue dissolved in water (solution No. 2). Solution No. 1 contains any oxalic acid which may have existed free in the substances examined No. 2 that which existed in the form of soluble oxalates. If lime or magnesia have been administered as an antidote, the substances must be boiled for an hour or two with potassium carbonate (not the hydroxid), filtered, and the filtrate treated as above. In the solutions so obtained, oxalic acid is characterized by the tests given above. The urine is also to be examined microscopically for crystals of calicum oxalate. The stomach may contain small quantities of oxalates as normal constituents of certain foods. 

Only the more important of the numerous publications of Fourcroy can be mentioned many are on medical subjects and he was the originator of modem pathological chemistry. He analysed many drugs and mineral waters and laid stress on the value of chemistry in medicine and pharmacy, but avoided a one-sided enthusiasm in this region. He gave a chemical classification of mineral waters into acidulous, saline, sulphurous and fermginous, each class being subdivided so as to make nine orders and describes their chemical analysis. ... 

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