the purplish colour produced soon fades, however, and at the end of a year a pale grey remains. Acid magenta becomes duller but not bluer. The rhodamines, pyronin G, and acridine red become yellower. Cloth red 3 G extra and 3 B extra become distinctly yellower; ponceau 2 S extra becomes much bluer. Cam-wood red is remarkable for becoming quite brown and appearing, therefore, darker at the end of the first fading period. This colour soon fades, however, and leaves at the end of a year a pale drab tint. CLASS III. MODERATELY FAST COLOURS. (WOOL.) The colours of this class show distinct fading at the end of the second period (June 14 to July 21, 1892), which becomes more pronounced at the end of the third period (July 21 to August 14, 1892). A pale tint only remains at the end of the fourth period (August 14 to February 16, 1893), and at the end of a year's exposure the colour has entirely faded, or, at most, mere traces of colour remain. Wool Book I. Azo Colours. Acid Reds. 3. Scarlet G. From xylidine and B-naphthol-di-sulphonic acid R. S. and J. 49. 5. Brilliant Scarlet GG. From m-xylidine and B-naphthol-di-sulphonic 11. Scarlet GR. From xylidine and B-naphthol-mono-sulphonic acid S. S. and J. 47. 14. Lake Scarlet R. Same as 3. 15. Ponceau R. 17. Scarlet R. acid R. From p- and m-xylidine and B-naphthol-di-sulphonic 21. Scarlet 2 R. Same as 5. 22. Double Brilliant Scarlet 2 R. 23. Pyrotin Red 3 RO. From B-naphthylamine-sulphonic acid D and a-naphthol-mono-sulphonic acid C. 25. Persian Red. 27. Croceïn Scarlet OXF. From naphthionic acid and B-naphthol-monosulphonic acid B. S. and J. 86. 28. Ponceau 2 R. From amido-azo-benzene and B-naphthol-mono-sulphonic acid B and S. S. and J. 108. 29. Cochineal Scarlet 2 R. From toluidine and a-naphthol-mono-sulphonic acid C. S. and J. 40. 31. Cochineal Scarlet 4 R. From xylidine and a-naphthol-mono-sulphonic acid C. S. and J. 45. 32. Ponceau 3 R. From amido-ethyl-dimethyl-benzene and B-naphthol-disulphonic acid R. S. and J. 51. 33. Coccin BB. 34. Naphthol Scarlet. acid. 37. Cochineal Scarlet R. From naphthionic acid and B-naphthol-sulphonic 38. Anisol Red. From ortho-anisidine and B-naphthol-mono-sulphonic acid S. S. and J. 54. 39. Ponceau 4 R. From cumidine and B-naphthol-di-sulphonic acid R. S. and J. 51. 40. Azo-eosin. From ortho-anisidine and a-naphthol-mono-sulphonic acid NW. S. and J. 55. 41. Coccinin. From ortho-amido-phenetol and B-naphthol-di-sulphonic acid R. S. and J. 41. 49. Crystal Ponceau. From a-naphthylamine and B-naphthol-di-sulphonic acid G. S. and J. 64. Fast Red E. From naphthionic acid and B-naphthol-mono-sulphonic acid S. S. and J. 87. 52. Cloth Scarlet 64. Fast Red C. acid NW. 66. Croceïn B. acid Sch. G. From naphthionic acid and a-naphthol-mono-sulphonic From amido-azo-benzene and a-naphthol-di-sulphonic 67. Cloth Red G. extra. From amido-azo-toluene and B-naphthol-mono- 69. Bordeaux G. From amido-azo-toluene-mono-sulphonic acid and B-naphthol-mono-sulphonic acid S. S. and J. 126. 70. Orchil substitute G. From para-nitraniline and B-naphthylamine-monosulphonic acid Br. S. and J. 37. 71. Granat liquid. From a-naphthionic acid and a-naphthol-di-sulphonic acid (3.6). 72. Cloth Red No. OG. Same as 67. 75. Buffalo Rubin. From a-naphthylamine and a-naphthol-di-sulphonic acid Sch. S. and J. 61. 77. Enanthin. From naphthionic acid and naphthol-di-sulphonic acid. 81. Fast Red D. From naphthionic acid and B-naphthol-di-sulphonic acid R. S. and J. 89. 86. Palatine Red. From a-naphthylamine and naphthol-di-sulphonic acid. S. and J. 66. Induline Colours. Rosindulines. 78. Rosinduline B. Constitution not published. Wool Book II. Natural Colouring Matters. Acid Reds. 3. Cochineal crimson (alumina mordant). 4. Kermes crimson (alumina mordant). CLASS IV. FAST COLOURS. (WOOL.) The colours of this class show comparatively little fading during the first, second, and third periods. At the end of the fourth period a pale shade remains, which at the end of the year's exposure still leaves a pale 2. Ponceau 2 G. Azo Colours. From aniline and B-naphthol-mono-sulphonic-acid S. From aniline and B-naphthol-di-sulphonic acid R. From toluidine and B-naphthol-di-sulphonic acid R. S. and J. 29. S. and J. 46. Constitution not published. From xylidine and a-naphthol-di-sulphonic acid Sch. 18. Azo Coccin 2 R. From xylidine and a-naphthol-mono-sulphonic acid NW. S. and J. 44. 19. Brilliant Croceïn MOO. From amido-azo-benzene and B-naphthol-disulphonic acid y. S. and J. 109. Wool Book I. Acid Reds. 20. Palatine Scarlet. From m-xylidine and naphthol-di-sulphonic acid. S. and J. 48. 24. Cotton Scarlet NT. From amido-azo-benzene and B-naphthol-disulphonic acid G. 26. Croceïn Scarlet 3 B. From amido-azo-benzene-mono-sulphonic acid and B-naphthol-mono-sulphonic acid B. S. and J. 120. 35. Double Brilliant Scarlet 3 R. From B-naphthylamine-sulphonic acid 44. Fast Ponceau B. From amido-azo-benzene-di-sulphonic acid and B-naphthol. S. and J. 121. 45. Milling Red FR. Constitution not published. 46. Erythrin X. From amido-azo-benzene and B-naphthol-tri-sulphonic 47. Croce in Scarlet 7 B. From amido-azo-toluene-mono-sulphonic acid 51. Phoenix Red A. Constitution not published. 53. Cloth Red G. acid and From amido-azo-benzene and a-naphthol-mono sulphonic acid NW. S. and J. 106. 55. Ponceau 6 R. From naphthionic acid and B-naphthol-tri-sulphonic acid. S. and J. 90. 56. Coccinin B. From amido-p-cresol-methyl-ether and B-naphthol-disulphonic acid R. S. and J. 56. 57. Brilliant Croceïn 9 B. Constitution not published. 63. Croceïn AZ. From amido-azo-benzene and a-naphthol-di-sulphonic acid. 65. Erythrin P. From amido-azo-benzene and an unknown naphtholsulphonic acid. 85. Croceïn 3 B. From amido-azo-toluene and a-naphthol-di-sulphonic acid Sch. S. and J. 112. 87. Cloth Red B. From amido-azo-toluene and a-naphthol-mono-sulphonic acid NW. S. and J. 115. 91. Orseillin BB. From amido-azo-toluene-mono-sulphonic acid and a-naphthol-mono-sulphonic acid NW. S. and J. 124. 93. Cloth Red No. OB. From amido-azo-toluene and B-naphthol-disulphonic acid R. S. and J. 114. 97. Azo Fuchsin G. From sulphanilic acid and di-oxy-naphthalene (1.8)-a-mono-sulphonic acid. S. and J. 229. 98. Azo Fuchsin B. From toluidine and di-oxy-naphthalene (1·8)-a-monosulphonic acid. S. and J. 228. Wool Book II. Acid Reds. 95. Azo Carmine. Sodium salt of phenyl-rosinduline-di-sulphonic acid. S. and J. 369. CLASS V. VERY FAST COLOURS. The colours of this class show a very gradual fading during the different periods, and even after a year's exposure a moderately good colour remains. Oxyquinone Colours. 5. Alizarin Red (alumina mordant). 10. Alizarin Turkey Red (cotton). Natural Colouring Matters. 6. Madder red (alumina mordant). SILK PATTERNS. The foregoing colours were dyed on silk, employing 2 per cent. colouring matter, and the patterns were exposed to light, along with those on wool, with the result that the relative fastness of the various colours was practically the same as on wool. GENERAL RESULT. The experiments extend at present over too limited a number of colouring matters to enable one to draw fixed general conclusions, but it may be well already at this point to record the following observations. The most fugitive reds on wool and silk are the eosins and allied colours. Curiously enough, the introduction of the methoxy group, as in methyl-eosin, &c., increases the fastness, not of the colour as a whole, but of the pale faded tint which results after the first few weeks' exposure. As already stated, this tint remains practically unchanged even after a whole year's exposure. This is specially noticeable on the silk patterns. With respect to the rosindulines, it is interesting to note that the G shades are very fugitive, while the B shades are moderately fast. All basic reds belong to the more or less fugitive class, including, namely, the magentas, safranines, and rhodamines. The nature of the acid with which the colour base is combined seems to have no influence upon the fastness of the dyed colour. Comparatively few (about twenty) of the azo reds examined are fugitive, and these belong chiefly to the simple monazo colours. The great bulk of the fast and moderately fast reds belong to the azo colours, the so-called secondary disazo colours being generally faster than the rest. It is evident, however, that the fastness of these azo colours depends, not only upon the base which is azotised, but also upon the character of the naphthol-sulphonic acid employed. This is especially noticeable in the chromotropes, in which a particular dioxynaphthalene disulphonic acid is employed, and all of which are remarkable for their fastness. The particular azo compound and phenol united together is also of importance. With respect to the milling and cloth reds, it does not appear that the use of mordants with them increases their fastness to light. The number of very fast reds is extremely limited, but it includes both natural and artificial dyes-namely, madder, cochineal, kermes, alizarin, and the chromotropes 2 R and 2 B. When it becomes possible to expose the Congo reds, one or two others will no doubt have to be added to the list of very fast artificial red dyes. In this connection it may be pointed out that certain reds obtained from the natural dye-stuffs are fugitive, namely, those obtained from Lima-wood, Cam-wood, and the allied woods. It is well to add that there are no sharp lines of division with respect to fastness to light among the various reds, and each of the five classes into which they have been here arbitrarily divided includes colours which differ from each other more or less in this respect. The Action of Light on the Hydracids of the Halogens in presence of Oxygen.-Report of the Committee, consisting of Dr. W. J. RUSSELL, Captain W. DE W. ABNEY, Professor W. N. HARTLEY, Professor W. RAMSAY, and Dr. A. RICHARDSON (Secretary). SINCE the last report was presented the attention of the Committee has been directed to a consideration of the conditions necessary to start the decomposition of moist gaseous hydrogen chloride, and of aqueous solutions of the acid when exposed to the combined influence of sunlight and oxygen. It has been repeatedly noticed that, although decomposition of the gaseous mixture, when once started, proceeds at a fairly uniform rate in different samples, yet the time of exposure necessary to start the decomposition varies within very wide limits, although the conditions under which exposure is made appear to be the same in each case. It was also noticed that there was more difficulty in starting decomposition in hard than in soft glass tubes. This seems to indicate that the nature of the glass itself materially affects the initial stage of decomposition, which is dependent upon the length of time during which the acid has been kept in contact with the glass, as is borne out by such results as the following. Nine glass tubes having been filled with aqueous solutions of the acid of varying strength were exposed to sunlight. At the end of six months it was found that the most concentrated of these solutions had been decomposed, the others being unchanged, while after twelve months the three strongest of the remaining solutions showed by their yellow colour that they also had been decomposed. This is quite explicable on the ground that the stronger acid more rapidly dissolves out the constituents of the glass, and suggested that the presence of some metallic chloride is required to start the decomposition of the acid. Following up this line a large number of experiments have been made on the influence of metallic chlorides in promoting decomposition, and, although the results are not sufficiently advanced to allow of our giving full details at present, they appear fully to bear out the above hypothesis. For instance, it was found that the addition of a minute quantity of pure dry alumina to a tube containing moist hydrogen chloride and oxygen brought about rapid decomposition of the acid on exposure to light, while precisely similar samples to which no alumina had been added remained stable for long periods. The Investigation of Isomeric Naphthalene Derivatives.-Seventh Report of the Committee, consisting of Professor W. A. TILDEN and Professor H. E. ARMSTRONG (Secretary). (Drawn up by Professor ARMSTRONG.) In previous reports attention has been over and over again directed to the alpha-law of substitution as the dominant law in the case of naphtha |