^{page 561 note *} Let us state at once that in this memoir all atomic weights are referred to O = 16. For the atomic weights of potassium, ammonium, and chlorine we adopt Stas' numbers, as calculated by Lothar Meyer and Seubert; K = 39·136; NH₄ = 18·056; Cl = 35·455.

^{page 562 note *} “Challenger Reports,” Physics and Chemistry, vol. i., published by order of Her Majesty's Stationery Office, &c. Adam and Charles Black (and others).

^{page 562 note †} A good deal of black iridium remained.

^{page 563 note *} Specially made from pure (Trommsdorff's) carbonate-crystals, in a nickel basin.

^{page 566 note *} The silver solution and a volumetric deci-normal solution of sulphocyanate.

^{page 568 note *} Sometimes a film of platinum adheres firmly to the sides of the flask. This is easily recovered by dissolving it in aqua regia, evaporating to dryness in a porcelain crucible, and igniting the residue.

^{page 576 note *} Meaning a solution containing so many centigrammes of metallic platinum per c.c.

^{page 578 note *} The water determination in Experiment III. forms an exception, in this sense, that the substance was heated in a current of nitrogen, and the products filtered through a stopper of copper gauze (instead of metallic silver).

^{page 579 note *} No doubt some COCl₂ had been produced from the CO and AgCl, and not all been decomposed by the silver spiral, although we operated at the highest temperature permissible in a Bohemian glass tube.

^{page 580 note *} We mean the bulk of the original precipitate; i.e., that part of it which did not pass on the filter, and which, as stated on page 570, amounted to 9·6244 grms. after drying at 130°C.

^{page 581 note *} And a small slip in a calculation; the correctly calculated value is 196·64.

^{page 582 note *} The AgCl in the titrations had a tinge of pink indicating platinum.

^{page 582 note †} Including the 0·87 mg. from the distillate.

^{page 582 note ‡} Instead of 194·93, as found for “E.”

^{page 584 note *} This second experiment was earned out for us by Mr James Robson.

^{page 585 note *} Made each out of two lipless test-tubes sliding over one another.

^{page 588 note *} “P” stands for weight of platinum used as chloroplatinic acid, per 2KCl parts.

^{page 589 note *} Per 1 grm. chloride of potassium as calculated from the platinum, assuming Pt to correspond to 2KCl.

^{page 592 note *} “Ether alcohol,” in connection with Finkener's method, always means 1 volume of anhydrous ether and 2 volumes of absolute alcohol.

^{page 593 note *} For details, see “Challenger Memoirs,” Physics and Chemistry, vol. i. (appendix), p. 233Google Scholaret seqq.

^{page 593 note †}

^{page 594 note *} We subsequently came to prefer the perchlorate for obvious reasons.

^{page 595 note *} K = 39; Cl = 35·5; Pt = 198.

^{page 595 note †} K = 39·13; Cl = 35·454; Pt = 194·8.

^{page 597 note *} We adopted this word for designating the operation described.

^{page 598 note *} Meaning a solution containing 5 centigrms. of platinum metal per c.c. The phrases “5 per cent.,” “10 per cent.,” &c, platinum solution must be read in this sense.

^{page 599 note *} Determined by a blank carried out on a large scale.

^{page 601 note *} Finkener does not say it is; but for a time it was our method.

^{page 602 note *} For mode of preparation, see “Challenger Memoir,” p. 16.

^{page 603 note *} See last line of this page.

^{page 603 note †} The designations of the following sets of experiments do not in general indicate the order in which they were carried out.

^{page 603 note ‡} Meaning a mixture containing 95 parts of chloride of potassium in 100 of total anhydrous salts.

^{page 604 note *} In only one case, No. (4), did the filtrate contain a trace of platinum. It was recovered by H₂S, the PtS₂ made into Pt, and its weight (0·4 mg.) added on.

^{page 607 note *} As communicated by him to a Committee of the British Association, and published by them in a Report presented to the Meeting at Glasgow, in 1876.

^{page 608 note *} We used to be under this erroneous impression ourselves until some three years ago, when we analysed a carefully prepared platinum solution (which had been specially freed from extra hydrochloric acid) for chlorine and platinum. It contained very nearly 6 × Cl for 1 × Pt, which, by the way, is in accordance with an old analysis of “chloride of platinum,” quoted in Gmelins's handbook as having been made by Vauquelin.

^{page 610 note *} These factors were calculated from results for “M” in the first series of potassium experiments. We did not consider it necessary to recalculate the analyses with our present factors.

^{page 611 note *} Those of (4) were lost by a disaster in the laboratory.

^{page 614 note *} From the one analysis of this set in which Tatlock's directions were strictly obeyed.

^{page 621 note *} A weighed portion of the filtrate from the platinum evaporated to dryness, and made neutral, as above explained, and weighed. Actual weight = ·2213 grm. for the fraction analysed. The salt was analysed, and found to contain 29·09 per cent, of chlorine, i.e., almost exactly as much as the original chloride of rubidium.

^{page 631 note *} This experiment was carried out for us by Mr James Robson.