^{page 529 note *} Michaelis, , Berichte, x. (1877) p. 807Google Scholar.

^{page 529 note ‡} Hofmann, , Berichte, v. (1873) p. 110Google Scholar.

^{page 529 note ∥} Michaelis, , Berichte, vii. (1874) p. 1070Google Scholar.

^{page 529 note †} Michaelis, and Panek, , Annalen, 212, p. 234Google Scholar.

^{page 529 note §} Hofmann, , Berichte, vi. (1873) p. 303Google Scholar.

^{page 529 note ¶} Hofmann, , Berichte, iv. (1871) pp. 433 and 609Google Scholar.

^{page 530 note *} Hofmann, , Berichte, iv. (1871) pp. 433 and 610Google Scholar.

^{page 530 note ‡} Hofmann, , Berichte, iv. (1871) pp. 433 and 610Google Scholar.

^{page 530 note †} Michaelis, , Berichte, x. (1877) p. 810Google Scholar.

^{page 530 note §} Michaelis, and Dittler, , Berichte, xii. (1879) p. 338Google Scholar.

^{page 531 note *} Hofmann, , Berichte, v. (1872) p. 104,Google Scholar and vi. (1873) p. 303.

^{page 533 note *} Meyer, , Berichte, iv. (1871) p. 734Google Scholar.

^{page 533 note ‡} Michaelis, and Czimatis, , Berichte, xv. (1882) p. 2018Google Scholar.

^{page 533 note ∥} Brühl, , Annalen, 177, p. 214Google Scholar.

^{page 533 note †} Hofmann, , Proc. Boy. Soc., xi. p. 530Google Scholar.

^{page 533 note §} Letts, , these Transactions, xxx. part 1, p. 285Google Scholar.

^{page 534 note *} Czimatis, Berichte, xv. (1882) p. 2016Google Scholar

^{page 534 note †} Hofmann, , Phil. Trans., 1860, p. 431Google Scholar.

^{page 536 note *} Letts, and Collie, , (1) these Transactions, xxx. part 1, p. 213;Google Scholar and (2) Phil. Mag., August 1886.

^{page 536 note †} Collie, (1) Chem. Soc. Jour., 1888, p. 636; and (2) Ibid., p. 714.

^{page 537 note *} Brown, Crum and Letts, , these Transactions, xxviii. p. 371;Google ScholarLetts, , these Transactions, xxx. p. 285Google Scholar.

^{page 537 note †} Hofmann.

^{page 537 note ‡} Masson, and Kirkland, , Chem. Soc. Jour., 1889 (Trans.), p. 126.CrossRefGoogle Scholar

^{page 537 note §} Dobbin, and Masson, , Chem. Soc. Jour., 1885 (Trans.), p. 56, and 1886, p. 846.CrossRefGoogle Scholar

^{page 538 note *} Thenard, , Comptes Rendus, xxi. p. 144,Google Scholar and xxv. p. 829.

^{page 538 note †} Michaelis, , Berichte, x. p. 807Google Scholar.

^{page 538 note ‡} Michaelis, , Berichte, vii. (1875) p. 499Google Scholar.

^{page 539 note *} Michaelis, , Berichte, xi. (1878) p. 885Google Scholar.

^{page 539 note †} Girard, , Ann. de Chim. und de Phys. [vii.], ii. p. 50Google Scholar.

^{page 539 note ‡} Messinger, and Engels, , Berichte, xxi. (1888) p. 328Google Scholara and p. 2919a.

^{page 540 note *} Hofmann, , Berichte, v. (1872) p. 100Google Scholar.

^{page 547 note *} Köhler, and Michaelis, , Berichte, x. (1877) p. 810Google Scholar.

^{page 547 note †} Michaelis, and Panek, , Annalen, 212, p. 234Google Scholar.

^{page 547 note ‡} Moslinqer, , Berichte, ix. (1876) p. 1008Google Scholar.

^{page 554 note *} Letts, , these Transactions, xxx. part 1, p. 285Google Scholar.

^{page 557 note *} Mean of ten determinations of different preparations of the compound. The extremes were 25·9 to 27·2.

^{page 557 note †} An old analysis by one of us and Collie, N., these Transactions, xxx.Google Scholar part 1.

^{page 557 note ‡} Mean of three determinations.

^{page 565 note *} At first we thought it possible that the dibenzyl phosphinic acid might have owed its origin to the action of the potash solution on oxide of tribenzyl phosphine (see p. 558). But that this reaction does not occur when oxide of tribenzyl phosphine is boiled with caustic potash solution, we proved by an actual experiment.

^{page 567 note *} The hydrogen is no doubt too high, as the combustion tube was not warmed, and cold oxide of copper was used—both no doubt containing hygroscopic moisture.

^{page 568 note *} Prepared by a very simple method discovered by us, namely, by saturating benzyl alcohol with dry hydriodic acid and washing the product with water when it solidifies. The yield appears to be quantitative.

^{page 568 note †} A large excess of the primary phosphine was therefore employed, as the molecular weight of C₇H₇I is 218, while that of C₇H₇PH₂ is 124; so that, roughly speaking, 2 parts of the former is required for 1 of the latter.

^{page 569 note *} Distilled from phosphoric anhydride.

^{page 570 note *} The dibenzyl phosphinic acid was identified by its melting point (191°·5–192°) after recrystallisation. The oxide of tribenzyl phosphine by its characteristic crystalline form and by the production of its crystalline compound with bromine in acetic acid.

^{page 573 note *} The rest of the product was evaporated down with aqueous potash, and also yielded oxide of tribenzyl phosphine in abundance, some benzyl phosphinous acid, but scarcely a trace of dibenzyl phosphinic acid.

^{page 574 note *} Letts, and Collie, , these Transactions, xxx.Google Scholar part 1.

^{page 574 note ‡} Michaelis, , Berichte, xv. (1882) 801AGoogle Scholar.

^{page 574 note ¶} Letts and Collie, loc. cit., p. 181.

^{page 574 note ‡} Ledermann, , Berichte, xxi. (1888) 405AGoogle Scholar.

^{page 574 note §} Letts and Collie, loc. cit.

^{page 574 note ∥} Letts and Collie, loc. cit.

^{page 575 note *} Ledermann, , Berichte, xxi. (1888) 405AGoogle Scholar.

^{page 575 note †} We are of opinion that when this compound is crystallised from alcohol, the crystals have the formula 2(C₇H₇)₄PI,C₂H₆O.

^{page 579 note *} Proceedings, 1887, p. 82.

^{page 589 note *} Comptes Rendus, xxi. p. 144, and xxv. p. 892.

^{page 589 note †} Hofmann, and Cahours, , Phil. Trans., 1857Google Scholar; and Ann. de Chim. et de Phys. (3), lxi. p. 5Google Scholar.

^{page 589 note ‡} Berlè, , Jour. f. Prac. Chem., lxvi. p. 73Google Scholar.

^{page 590 note *} Berlè, , Comp. Rend., xlixGoogle Scholar.

^{page 590 note †} Cahours, , Comp. Rend., xlix. p. 87;Google Scholar and Jahresbericht, 1859, p. 430.

^{page 590 note ‡} Letts, and Collie, , these Transactions, xxx. part 1, p. 181Google Scholar.

^{page 590 note §} Hofmann, and Cahours, , Ann. de Chim. et de Phys. (3), liGoogle Scholar.

^{page 590 note ∥} Hofmann, Ibid., lxii., lxiii., lxiv.

^{page 591 note *} Hofmann, , Berichte, iv. (1871) 205Google Scholar.

^{page 592 note *} Hofmann, , Berichte, iv. (1871) p. 209Google Scholar.

^{page 592 note ‡} Ibid., Berichte, vi. (1873) p. 292Google Scholar.

^{page 592 note ∥} Ibid., Berichte, vi. (1873) p. 297Google Scholar.

^{page 592 note **} Drechsel, and Finkenstein, , Berichte, iv. (1871) p. 352Google Scholar.

^{page 592 note †} Hofmann, , Berichte, iv. (1871) p. 205Google Scholar.

^{page 592 note §} Ibid., Berichte, vi. (1873) p. 296.

^{page 592 note ¶} Ibid., Berichte, iv. (1871) p. 372.

^{page 592 note ††} Hofmann, Berichte, iv. (1871) p. 372Google Scholar.

^{page 593 note *} Hofmann, , Berichte, iv. (1871) p. 430Google Scholar.

^{page 593 note ‡} Ibid., vi. (1873) p. 292.

^{page 593 note ∥} Ibid., vi. (1873) p. 297.

^{page 593 note **} Ibid., Berichte, v. (1872) p. 100.

^{page 593 note †} Hofmann, Ibid., iv. (1871) p. 605.

^{page 593 note §} Ibid., vi. (1873) p. 296.

^{page 593 note ¶} Ibid., v. (1872) p. 100.

^{page 594 note *} Berickte, vi. (1873) 601;Google Scholar viii. (1875) 922; xii. (1879) 1009.

^{page 594 note ‡} Annalen, 212, pp. 203 and 209.

^{page 594 note ∥} Berichte, ix. (1876) 1051Google Scholar.

^{page 594 note †} Berichte, xiii. (1880) 653Google Scholar.

^{page 594 note §} Ibid., xiii. (1880) 2174.

^{page 594 note ¶} Ibid., xvii. (1884) 1273.

^{page 595 note †} Berichte, viii. 1304.

^{page 595 note §} Michaelis and Gleichmann, Ibid., p. 820.

^{page 595 note ‡} Michaelis, and Gleichmann, , Berichte, xv. (1882) p. 801Google Scholar.

^{page 602 note *} This was well washed, dissolved in baryta, and the solution added to the baryta extracts.

^{page 603 note *} In the meantime we had obtained benzyl phosphinous acid from other sources, and had become acquainted with some of its properties. Among them, we had ascertained that it yields the primary phosphine when heated.

^{page 603 note †} One of us and N. Collie have shown that the haloid salts of tetrabenzyl phosphonium are decomposed when treated with an alkali, and yield the tertiary phosphine oxide (see p. 575).

^{page 609 note *} As we have mentioned on p. 585, it is possible that other oxidised derivatives exist, but the above are the most important.

^{page 612 note *} Michaelis, and Ananoff, , Ber., vii 1688;Google Scholar and Kohler, and Michaelis, , Ber., x. 807Google Scholar.

^{page 613 note *} By the oxide of copper method.

^{page 617 note *} Not absolutely pure, but recrystallised two or three times from the crude product.

^{page 617 note †} A very pure specimen of the acid, which had been obtained from the barium salt, and was snow-white.

^{page 618 note *} Michaelis, and Matthias, (Ber., vii. 1070)Google Scholar and Michaelis, (Annalen, 181, p. 323)Google Scholar found that the corresponding phenyl phosphinic acid, when heated to 200° C., loses sufficient water to give the pyro acid analogous to the one we obtained, viz., (C₆H₅)₂H₂P₂O₅; while at 210° G. three molecules of the acid lose two molecules of water, giving, they suppose, (C₆H₅)₃H₂P₃O₇. They did not succeed in isolating either of the pyro acids or in obtaining their salts, as they re-hydrate when treated with water.

^{page 620 note *} The combustion was made with pure oxide of copper, and the phosphorus determined as described at p. 556.

^{page 620 note †} We do not know to what these are due.

^{page 620 note *} The salt was distilled with caustic potash and the ammonia which was evolved absorbed by hydrochloric acid and precipitated as chloroplatinate, the latter being subsequently ignited, and the ammonia calculated from the weight of platinum left.

^{page 623 note *} The quantities required for the equation (C₇H₇)₂HPO₂+PCI₅=(C₇H₇)₂POCI + HCI + POCI₃ are 10 grms. of the acid and 8.5 grms. of pentachloride of phosphorus.

^{page 624 note *} Fsleisner, , Berichte, xiii. (1880) 1665Google Scholar.

^{page 624 note ‡} Letts and Blake, this communication, p. 554.

^{page 624 note ∥} Ledermann, , Berichte, xxi. (1888) 405Google Scholara.

^{page 624 note **} Letts and Collie, loc. cit., p. 215.

^{page 624 note †} Letts, and Collie, , these Transactions, xxx. part 1, p. 202Google Scholar.

^{page 624 note §} Letts and Blake, this communication, p. 599.

^{page 624 note ¶} Letts and Collie, loc. cit., p. 196.

^{page 624 note ††} Letts and Blake, this communication, p. 574.

^{page 625 note *} Analyses 1–5 were made by Letts and W. Wheeler, and from 6-8 by Letts and Blake, and the preparations-obtained in both cases from Hofmahn's “dibenzyl phosphine” (see p. 554). Analyses 9–11 were made by Letts and Collie, the preparation being made from the oxide obtained from the products of the action of sodium phosphide on benzyl chloride.

^{page 626 note *} Collie, , Chem. Soc. Jour., 1889, p. 227Google Scholar

^{page 626 note †} Letts and Collie, loc. cit.

^{page 626 note ‡} Fleissner, loc. cit.

^{page 627 note *} The discovery of the nitro compound was made independently by Dr Collie and ourselves.