121 NOTE ON THE EXAIMINATION OF SPIRITUS ZTHERIS NITROSI, BY A. DUPRE, PILD., F.R.S. Rend bpforc tlrr Society of Pidlic Ana71~sts. cn Pt7b Jtinc, 1879. HAVING a t various times been asked for esplanatioiis as to the method I use for estimating tlie amount of nitrous ether, contained in a snrnple of Spiritus Etheris Nit8rosi, I take this opportunity of describing the mctliod 01x8 for dl. The principle of the method will be found in Duflos Apothekerbzcc7~, Edition 1867, p.251, and I have simply worked out tlic details a little more fully. For the present I confine myself to the analytical method, and must leave inany points of interest connected with tho subject to some future time. Spiritus atheris Nitrosi, as is mll lmo~m, is d&cted to be prepared (firit. PlLam.) by distilling a niixture of spirit, nitric and sulphnric acids a i d copper, and mixing the distillate obt'nined mitli n certain proportion of spirit.If a11 the nitric acid employed were used 1113 in tlie foormnt8ioii of nitrous ether, tlic proportion of sach contained in the finialiecl lxodnct, if ti\-o pints of spirit me added to the 15 ozs. of distillate, would snioimt to aborrt 6.5 per cent.In practice this result is, however, never obtained ; and, according to my experience, ve may consider a prodLlct containing 3 per cent. of iiitrous ether as fairly representing the B.P. preparation. In judging of the purity, or otherwise, of any given sample of Spiritus Bthcris Nitrosi, B.P., the particular method of manufacture adopted iii the preparation of the122 THE ANALYST.sample is, of course, perfectly immateilial ; as long as it fairly corresponds in strength to tlre B.P. standard, it must be considered ns of tlie nature, substance and quality cle man ci e d , 11 ow ever produce cl , Charactws. B,P, Transparent, very slight tinge of yellow. Specific gravity, 01845. Effervesces feebly, or not at all, when diaken with a little bicarboilate of soda, When agitated with a solution of salphate of iron, a i d a few drops of r;ulplruric ncici, it becomes olive browi or blaclr, If it be agitated with tvice its volame of saturated solutioii of chloride of calicum in a closed tube, two per cent.of its original ~ o l ~ m e szparate in tlie form of nitrous etlier, and rise to tlie surface of the mixture, Should give no precipitate with nitrate of silver ; absence of hydrocyanic and formic acids.A sniall qnantity poured on a little water, and ignited, should lem-e an aqueous solution, which gives no precipitate with iiitrde of Rilver ; absence of hydrocliloric ether, chloride of ethylene, &c. The cliloride of calcium test is not of much value. Firstly, because only those samples respond to it wliicli are iicarly of tlre proper strength, and iio iiiformatioir is gained as to the composition of those samples, from which nothing separates, escept of course that they are below tlie propcr strength.Secondly, because the mbstance separating though chiefly, is not by airy nienirs only, nitrous etheil. The iroii test may be used as a rough quantitatim test by using a sample of lmomii strength for comparison, and it offers a very ready means, before n magistrate for example, to sliow the cliaracter of any impugned sample.Estimation of Xitrous Ether. Ten cubic centimetres of the ether are introduced into a small flask already containing about 1.5 grammes of solid potash hydrate. The flask is closed with a well-fitting cork, gently agitated from time to time to promote solutioii of the potash, and left standing over night.Nest day tlie contents of tlie flask, more or less yellow according to the amount of aldehyde present, are waslied into an evaporating basin with 50 C.C. of water, a i d the mixture evaporated on n water-bath to about half or one-third. The remainder is allowed to cool, filtered tlirough a little glass wool into a beaker made up to 300 C.C.with water, 50 c,c. of diluted sulpliuric acid (1 in 4) are added, a i d the nitrous acid present determined by a, standard solution of permanganate. This standard solution is prepared by dissolving 8.475 grammes of pure permanganate of potassium (or its equivalent) in one litre water; 1 C.C. of this solution is equivalent to 0.01 grammes of nitrous ether, and therefore indicates 0.1 per cent of nitrous ether, if 10 C.C.of ether have been taken. The decolonration of the permangannte is rapid at first, gradually becoming slower. As soon as this is perceived not more than 0.6 C.C. are added at a time, and tlie process must be considered as at an end if the solution still shows a distinct pink or red colouration two minutes after such addition.For every cubic centimetre of permanganate solutioii then used, the Spiritus Btheris Nitrosi contains, at a maximum, 0.1 per cent. of nitrous ether. The solution still continues to decolourise peimanganate, though but slowly, and much more will have to be added before the colouration becomes permanent. I have however convinced myself, by many experiments, that all nitrous acid present is oxidised when the above indicated point is reached, No doubt other substances are Further Tests of Pzwity .THE ANALYST.125 Feb. 21, 1872 Nov. 15, 1873 April 23, 1879 Dec. 2, 1873 April 15, 1879 oxidised as well, and tlie process indicates more nitrous ether than is actually present ; but as the error is on the side of leniency, it is perhaps an advantage rather tliaij otherwise.By following out strictly the directions here given, it mill be found that duplicate analyses of a sample rarely differ more than 0.1 per cent. from eacli other ; while, with poor samples, tlie agreement is even more perfect. Sliould a sample require much permanganate, a,nd the solution, instead of becoming colourless, remains brown or yellow, more sulphuric acid must be added.If, instead of evaporating and filtering the alcoholic solution, it is at once diluted, acidified, and permanganate added, more of the latter will be required than in tlie former case. In good samples the difference is sometimes great, but in most poor samples it is but alight, and in such case this more rapid process may be adopted. I have also tried the process of adding at once an excess of permanganate, letting stand five minutes and estimating the excess remaining, but the results given are decidedly too high. Various other methods have been proposed for the estimation of the nitrous ether, but I do riot propose to enter into such, as the process given fulfils, I believe, all necessary conditions.It is stated in most works on the subject that iiitrous ether is rapidly decomposed and becomes acid.The latter statement is correct, as far at least as ordinary Spiritus Xtlieris Nitrosi is concerned, but the former is not in accordance with my experience. Spiritus Xtheris Nitrosi becomes acid mainly on account of the oxidation of tlie aldehyde it contains, while the nitrous ether present suffers but slow decomposition, at least when dissolved in spirit of sufficient strength.The fallowing analyses will illustrate this. Sample I. was prepared by myself on February 21st, 1872, auii lins been kept ever since in a glass stoppered bottle (white glass) of oiie litre capacity tvliicli it filled about half at first. About one half of the neck of the bottle was broken off early in 1872, so that the stopper does not fit very tightly since.The bottle stood on a shelf in the laboratory exposed to ordinary diffused daylight, but never to direct sunlight. On the bench below, and near to where the bottle stands, a Bunseii gas burner is frequently in use. Sample 11. was bought as a sample of Spiritus Btheris Nitrosi (Brit. PlLam.) from a well known wholesale house on December 2nd, 1873.It was contained in tlie ordiiiary pint bottle of green glass, and stood ever since in cz cupboard of the laboratory, or in other words chiefly in the dark. Both bottles were frequently opened, and small portions of ether taken out in the intervals between tlie analyses given :- ,836 84.8 per cent. b. w. 0.10 2.00 *839 83.6 9 , 9 , 0.90 1-98 ,844 81.7 9 9 I , 0.85 0.89 ,824 89.5 $ 3 9 , 1.19 1.35 *847 80.5 9 9 9 9 1.38 0.96 No.of sample. We Corresponding Total acid free Real gravity. alcoholic strength. as acetic acid. nitrous ether. I I Date of I Specific I examination, see, therefore, that even uuder somewhat unfavowable conditions the124 THE ANALYST. decomposition of the nitrous ether proceeds but slowly, and the plea sometimes advanced by chemists that the sample of Spiritus Btlieris Nitrosi obtained at their shops, and found wanting, had been kept for some time and had decomposed, may safely be set aside as untrue.Iu conclusion, I give the analyses of a number of samples, every one of which mas bought as Spiritus Btheris Nitrosi (Brit. Phat*m.), and should therefore have had a sp.gr. of 0.845, and contained about 3 per cent. of nitrous ether. All, except the last, mere, however, bought before tlie present Sale of Food and Drugs Act came into operation. The last sample ~7as supplied to the Westminster Hospital early in April, 1879. The bottle coiltailling it, a Wiiichester quart, was labelled ‘ I Spiritus Btheris Nitrosi, Brit. Pliarm., sp. gr. 0.845.’’ The bottle was quite full, and had not been opened at the Hospital, the stopper being still tied over with bladder when I took the sample on April 23rd, 1879.Specific. Corresponding Total free acid Real gravity. alcoholic strength. as acetic acid. nitrous ether. 0.908 . . . . 54.05 per cent. b. w. 0.42 per cent. . . 0-23 per cent. 0.913 .. .. 52.0 .. .. 0.39 .. .. 0.19 0.851 ,. .. 79. .. .. 0.09 ,. .. 0.06 0,892 .. .. 61.5 .. a . 0.32 .. .. 0.38 (3.854 .. .. 77.7 .. .. 0.47 .. .. 0.44 0.936 .. .. 41.8 .. I . 0.41 .. .. iP10 0.851 .. .. 79. .. .. 1.14 .. .. 1.30 0.928 ,. .. 45.6 .. .. 0.33 .. .. 0.25 0.852 .. .. 78.5 .. .. 0028 .. .. 0-07 0.848 .. .. 80. .. .. 1.28 .. .. 1.40 0.849 .. .. 79.7 .. .. 0.96 .. .. 0.52 Mr. Hehner suggested that the direct addition of iodide of potassium would give a much fairer measure of the quantity of nitre present. He would add acetic acid and iodide of potassium, which both Dr. Muter and Mr. Wigner said they thought was a very good idea.