CHAPTER XLVI. UROPHANIC INORGANIC SUBSTANCES. 1. IODINE. In IODINE is frequently used as a medicine, sometimes rather indiscriminately. In other cases, its effects are irregular, though it has been given with a due regard to experience. It is necessary to ascertain the reasons of this variable action; and for this purpose the analysis of the urine will best serve. For one of the principal reasons why iodine and its preparations are borne very well by some, and have injurious effects in others, is the varying length of time required for its removal from the body. Thus Lehmann found that, when several persons had each taken a dose of 10 grains of iodide of potassium, some would immediately begin to excrete it in their urine, which after the lapse of twenty-four hours no longer contained any trace of the iodide. others, however, the iodide could frequently be found even after the lapse of three days. Supposing the daily dose of 10 grains to have been administered for a length of time to these two classes of people, the first class would most probably never have at one time more than 10 grains of the iodide in their body, while the latter might have 30 or 40 grains in their body at one time. Not only, therefore, would the action of the drug, in these latter cases, go parallel to the quantity present, but also it would last much longer; and in this way equal doses at equal intervals might in the latter class produce four times the effect they would produce in the first class. In some cases, therefore, where an explanation of an extraordinary mode of action of iodine or iodides may be necessary or desirable, the analysis of the urine will be the chief source for information on this point, due consideration being given to other excretions, by which iodine is removed from the economy. Volumetrical analysis of Iodine in the Urine. This method is based upon the fact, that a very dilute solution of iodine or an iodide yields all the iodine by distillation with sulphuric acid. In the distillate, the amount of iodine is determined by a solution of chloride of suboxyde of palladium of known strength. In the performance of this analysis, care must be taken never to have an excess of the solution of iodine mixed with the solution of palladium, as in that case the fluid does not get clear very quickly, and the precipitate of iodide of palladium adheres to the walls of the glass. But when the solution of palladium is present in slight excess together with a little hydrochloric acid, and the mixture is warmed to from 60° to 100° C. (140° to 212° F.), and agitated, the iodide of palladium, after a few seconds, separates in black, cheesy flakes, and the supernatant fluid is perfectly clear and colourless. In performing the analysis, therefore, to a known volume of the solution of palladium of known strength, such a volume of the solution of iodine to be analysed is added, as is just sufficient to precipitate the entire amount of palladium in solution. This analysis is so accurate, that th milligramme of iodine may be determined by means of the palladium, and 10th milligramme of palladium by means of iodine. The method is therefore, in one sense ten thousand times more delicate than chemical scales of the highest order. The chemical balance which I employ, one by Liebrich, at Giessen, will turn with th milligramme, when loaded with 100 grammes on each side. It therefore indicates one millionth of the weight which it is capable of carrying. The balance has therefore a disadvantage when compared with volumetrical analysis, in not being so able to combine quantity with accuracy; the dilution of tests enables us to produce a delicacy regarding quantities, which we might in vain endeavour to attain by mechanical appliances. Preparation of Solution of Iodide of Potassium of known strength. This solution is to be so graduated that every part of it contains Tooth part of iodine. For that purpose 1.308 Kersting, Ann. d. Chem. und Pharm.,' Bd. 87, p. 21. See also Neubauer, loc. cit., p. 120. grammes of dry iodide of potassium, perfectly free from iodate of potash, are dissolved in water, and the solution is diluted until amounting to one litre. 1 c.c. of this solution contains 1 milligramme of iodine, as 1.308 grammes of iodide of potassium contain 1 gramme of iodine. (126.88 165.991: x = 1.308.) Solution of Chloride of Suboxyde of Palladium of known strength. We prepare a solution of palladium of unknown strength, and graduate it by means of the solution of iodide of potassium, just described. 1 gramme of the metal is dissolved in aqua regia, with the aid of heat, and evaporated to dryness on the water-bath. After solution of the residue in 50 c.c. of concentrated hydrochloric acid, water is added to the amount of about 2000 c.c. The exact amount of palladium contained in a given volume is now determined by means of the solution of iodide of potassium of known strength, in the following manner. 10 c.c. of the solution of palladium to be graduated, are put into a balloon of about 200 c.c. capacity. The balloon is closed by a corkstopper, and warmed in a water-bath, to near boiling heat. From a burette, the graduated solution of iodide of potassium is now added, the mixture shaken, and warmed again. Four minutes will suffice to separate the mixture into a precipitate, which subsides towards the bottom of the vessel, and a clear supernatant fluid. Of the latter, two portions are each put in a test-tube. To the one portion, a few drops of the solution of iodide of potassium are added; and, by comparison with the other test-tube, we find whether a brownish tint has been produced by the iodide. In case a brownish precipitate has been produced, the two portions are again poured back to the main bulk of fluid, to which some more solution of the iodide is added under agitation, and warming, and so on, until in a fresh portion of the clear supernatant fluid no discoloration is produced by the addition of the iodide test fluid. At this stage of the proceeding, the fluid is separated from the precipitate by filtration; and, if a sample of it is not tinted brown by either solution of palladium or iodine, the fluid does not contain a trace of excess of either substance, and the analysis is completed. From the equivalent of the iodine used, the amount of palladium contained in the 10 c.c. used for analysis, may be found by calculation. 1 milligramme of iodine is equivalent to 0.42 milligrammes of palladium, which is therefore the quantity indicated by every cubic centimetre of the graduated solution of iodide of potassium. Supposing the 10 c.c. of solution of chloride of palladium required for the complete precipitation of palladium contained in it, 119 c.c. of graduated solution of iodide of potassium, containing 11.9 milligrammes of iodine, then the amount of palladium contained in the 10 c.c. of solution was 11.9 x 0.42 milligrammes=4.998 milligrammes. The same volume of solution of palladium would therefore require such an amount of solution of iodine of unknown strength, as would exactly contain 11.9 milligrammes of iodine. From the amount thus used, the amount of iodine contained in the entire bulk of fluid is ascertained by calculation. Application to the Urine. 100 c.c. or more of urine are mixed with 20 c.c. of concentrated sulphuric acid, and kept in a cold water-bath during the first violent evolution of heat. The balloon containing the mixture is then connected with Liebig's cooler, and the distillation proceeded with. It is continued until, in the neck of the balloon, white vapours of sulphuric acid begin to appear. If, however, the urine contains only a very small amount of iodine, any measured quantity, after addition of an excess of caustic potash, may be concentrated by simple evaporation of the water, and only then distilled with sulphuric acid in the manner described. The distillate thus obtained contains ioduretted hydrogen, all volatile acids of the urine, with carbonic, sulphurous, and sulphuric acids. The sulphurous acid must be oxydized, before the fluid can be subject to further analysis. This is effected in the following manner :-To the distillate are added one or two drops of solution of starch (made of 1 part of starch, th part of sulphuric acid, and 24 parts of water), and after that a saturated solution of chloride of lime in drops, until the fluid just begins to get blue. The blue colour is then again made to disappear by one or two drops of a dilute solution of sulphurous acid in water. The volume of the entire solution is now measured, and the necessary quantity of it filled into a Mohr's burette, and from this added to the 10 c.c. of solution of chloride of palladium in the manner above described, until the entire amount of palladium is precipitated. Thus, if 100 c.c. of urine yielded 96 c.c. of distillate, and if of this distillate 12 c.c. were required for precipitating the 4.998 milligrammes of palladium from the 10 c.c. of solution, then the 12 c.c. contain 11.9 milligrammes of iodine. (53·24: 126.88 = 4·998: x.) The 96 c.c. of distillate therefore, corresponding to 100 c.c. of urine, contain 8 x 11.9 milligrammes = 95.2 milligrammes, = 0.0952 grammes of iodine. 2. ARSENIC AND ANTIMONY. In cases where these metals, or either of them, should be present in urine in any considerable quantity, they would be precipitated as sulphides by a current of hydrothion conducted through the acidified liquid. But mostly their quantities are very small, not so much because those poisons are sparingly eliminated by the kidneys, as because (in cases of poisoning), the urine containing the largest proportion is mostly not to be obtained. When these substances have been administered to any person, either in medicinal doses, or by accident or criminal design, the urine of the patient voided some time afterwards, almost always contains some arsenic or antimony, so that Orfila was induced to recommend a diuretic treatment in cases of poisoning by either of these substances. Reinsch's Method of obtaining Arsenic and Antimony from Urine.1 The urine is evaporated to a small bulk, and then from one sixth to one seventh of its volume of pure hydrochloric acid is added to it. It is boiled; and while boiling, a small piece of thin copper foil, freshly brightened by rubbing with some oxalic or hydrochloric acid and paper, or a piece of fine copper-gauze, is introduced. Sooner or later, according to the quantity present, antimony, or arsenic, or both, are deposited on the copper, producing a blackish grey, or grey deposit, with a reddish-violet, or purple tint, if antimony in small quantities is deposited; but an iron grey or black tint, if antimony in large quantities, or arsenic, are deposited. If no deposit is observed at first, the whole of the liquid must be boiled down on the copper, before the inference is drawn, that arsenic or antimony are absent. If the copper be removed without any metallic tarnish or deposit upon its surface, there is no antimony or arsenic present. If it has ac 'Taylor, 'Guy's Hosp. Rep.,' October, 1857. |