[975] Ueber die Wirkungen des Aluminiums u. Berylliums, Inaug. Diss., Dorpat, 1886; Schmidt’s Jahrbuch, vol. ccxi. 128.
Siem’s research was made on frogs, cats, and dogs. For frogs he employed a double salt, consisting of sodic and aluminic lactate, to which he ascribed the formula Al2(C3H5O3)3(C3H4NaO3)3, equal to 15·2 per cent. of Al2O3. Twenty to thirty mgrms., administered by subcutaneous injection to frogs, caused death in from ten to twenty-four hours. After the injection there was restlessness, and, ultimately, general paralysis of the central nervous system. The circulation was not affected; the heart was the last to die.
For warm-blooded animals he used the double tartrate of sodium and aluminium. Beginning with a small dose subcutaneously administered, he gradually increased it, and found, under these circumstances, that the lethal dose for rabbits was 0·3 grm. per kilo. of body weight; for dogs 0·25 grm., and for cats 0·25 to 0·28 grm.; if, however, a single dose was administered, then cats could be killed by 0·15 grm. per kilo. The symptoms commenced ten to twelve hours after the injection of a large dose, but with a medium dose the symptoms might be delayed for from three to four days, then there was loss of appetite, constipation, emaciation, languor, and a disinclination to move. Vomiting and loss of sensation to pain followed, the power of swallowing even saliva was lost, and a condition supervened similar to bulbar paralysis. However true this picture may be when large doses are given subcutaneously, it does not follow that hydrate of alumina in small doses, given by the mouth, mixed with food, produces any symptoms whatever.
Alum baking-powders, containing from 30 to 40 per cent. of alum mixed with carbonate of soda, are in commerce, and have been for a long time, many tons being sold yearly. When water is added to such powders decomposition takes place, the result being sodic sulphate and aluminic hydrate, carbonic acid being given off. Were the hydrate, in small doses, capable of producing indigestion or disease of the central nervous system, it seems astonishing that, considering the enormous number of persons who use alum baking-powders, there should not be some definite evidence of its effect. The author and his family for months together have used alum baking-powders without any apparent injury, and there is little doubt that alumina hydrate passes out of the system mainly by the bowel, without being absorbed to any great extent. In a trial with regard to an alum baking-powder at Pontypridd (1893), the prosecution advanced the theory, and supported it by eminent scientific opinion, that aluminium hydrate was dissolved by the hydrochloric acid of the gastric juice, forming chloride of aluminium, some of which might be absorbed and enter the circulation; that which was not absorbed in the stomach passed on, and, meeting the alkaline fluids of the intestines, was again separated as aluminium hydrate, and as such absorbed.
If this does occur, still there is no direct evidence of its toxic influence in the small quantities used in baking-powder. It may be pointed out, also, that with regard to the possible lethal effect of a non-corrosive salt of alum, presuming that the lethal dose for man is the same as that for a cat, the amount of alumina to kill a 68-kilogramme man would have to be equal to 17 grms., or about 3 ozs. of ammonia alum. This important question can only be settled by careful feeding of animals carried on for a long period of time.
§ 898. Post-mortem Appearances.—In the few cases in which persons have been killed by large doses of alum or its salts there have been found corrosion of the mouth, throat, and stomach, and hyperæmia of the kidneys and intestine. In the animals experimented upon by Paul Siem, hyperæmia of the intestine, fatty degeneration of the liver and hyaline degeneration of the kidneys were the chief changes noted.
§ 899. Detection of Alumina.—In all operations for the detection of alumina, glass and porcelain vessels are to be avoided. The substances should be burned to an ash in a platinum dish, the ash treated with hydrochloric acid, the acid driven off by heat, and a few drops of nitric acid added, and dissolved in hydrochloric acid, and the solution boiled and filtered. If organs of the body are operated upon, iron and phosphoric acid will be present in the ash; this will, indeed, be the case with most organic substances. The filtered solution is boiled, and, while boiling, poured into a strong solution of sodic hydrate contained in a silver or platinum dish; the iron will now separate as oxide, and can be filtered off. To the filtrate is added a little sodic phosphate; it is then feebly acidified with hydrochloric acid, and ammonia added just sufficient to render it alkaline; a light whitish cloud of alumina phosphate, should alumina be present, is thrown down, and can be collected, thoroughly washed, dried, ignited, and weighed as alumina phosphate.[976] The alumina phosphate is then fused with sodic sulphate in a platinum dish or crucible, and the fused mass treated with hot water; the sodic phosphate dissolves, and the alumina oxide may be filtered off and dissolved in a little hydrochloric acid or sulphuric acid.
[976] One part of al. phosphate is equal to 0·42 Al2O3, 3·733 ammonia alum, and 4·481 potash alum.