Curves are given showing the relation between the direct sunlight (column 3) and diffuse daylight (column 4) in terms of the altitude. The curve of direct sunlight cuts the base line at 10°, showing that the conclusion formerly arrived at by one of the authors is correct, and that at altitudes below 10° the direct sunlight is robbed of almost all its chemically active rays. The relation between the total chemical intensity and the solar altitude is shown to be represented graphically by a straight line for altitudes above 10°, the position of the experimentally determined points lying closely on to the straight line. A similar relation has already* been shown to exist (by a far less complete series of experiments than the present) for Kew, Heidelberg, and Pará; so that although the chemical intensity for the same altitude at different places and at different times of the year varies according to the varying transparency of the atmosphere, yet the relation at the same place between altitude and intensity is always represented by a straight line. This variation in the direction of the straight line is due to the opalescence of the atmosphere; and the authors show that, for equal altitudes, the higher intensity is always found where the mean temperature of the air is greater, as in summer, when observations at the same place at different seasons are compared, or as the equator is approached, when the actions at different places are examined. The differences in the observed actions for equal altitudes, which may amount to more than 100 per cent. at different places, and to nearly as much at the same place at different times of the year, serve as exact measurements of the transparency of the atmosphere. The authors conclude by calling attention to the close agreement between the curve of daily intensity obtained by the above-mentioned method at Lisbon, and that calculated for Naples by a totally different method. * Phil. Trans. 1867, p. 555. II. "On the Acids contained in Crab-oil." By WILLIAM J. WONFOR, Student in the Laboratory of the Government School of Science, Dublin. Communicated by Dr. MAXWELL SIMPSON. Received March 7, 1870. Crab-oil is obtained from the nuts of a tree named by botanists Hylocarpus carapa, and also Carapa Guianensis. The tree grows abundantly in the forests of British Guiana; the oil is prepared by the Indians, who bring it to George Town for sale. The oil is obtained from the kernels by boiling them for some time, and then placing them in heaps and leaving them for some days; they are then skinned, and afterwards triturated in wooden mortars until reduced to a paste, which is spread on inclined boards and exposed to the sun; the oil is thus melted out, and trickles into receiving-vessels. As no investigation, so far as I have been able to ascertain, has ever been made of the acids contained in this oil, Professor Galloway, to whom I am indebted for the samples of the oil, recommended me to examine them; and the examination was conducted under his direction. The oil was in the state in which it is sold by the Indians; it possessed the appearance of a semifluid butyraceous mass, evolving a peculiar penetrating odour; its melting-point was 55° C. To obtain the acids, the oil was saponified with a solution of potassic hydrate, and the soap thus obtained dissolved in a large quantity of distilled water; to the solution sodic chloride was added in considerable excess; the soap which separated was washed and afterwards dissolved, and the solution treated with hydrochloric acid; the liberated fatty acids were collected and pressed, then melted in boiling water, and frequently washed to remove all traces of sodic chloride; the acids were again saponified, and again treated with sodic chloride, but the soda-soap was on this occasion decomposed with tartaric acid. The mixed acids had a melting-point of 40° C. The acids were dissolved in boiling alcohol of 89 per cent.; the solution, on cooling, deposited a white radiated crystalline mass, which was repeatedly recrystallized from alcohol until it acquired a constant melting-point; it was then saponified with a solution of potassic carbonate, and the solution of the mixed potash salts was evaporated to dryness on the water-bath; the fat salt was then dissolved in absolute alcohol. The alcoholic solution, unless extremely dilute, does not crystallize on cooling, but merely forms a strong jelly, which was, after pressing, dissolved in water, and the fat acid separated by a strong solution of tartaric acid; the separated acid was washed with boiling water until all potassic tartrate and tartaric acid were removed : it was subsequently twice crystallized from absolute alcohol: its meltingpoint was then found to be 57° C. The acid, when pure, presents the appearance of a white glistening radiated crystalline mass: two combustions were made; the acid employed in the two analyses was obtained from two different saponifications: I. 259 grm. gave 7115 CO, and 295 H,O=194 C and 0327 II. 2 These analyses, it will be seen, agree very closely with the formula for palmitic acid, C18 H32 O1. 16 Preparation of the Soda-salt.-The acid was saponified with a dilute solution of sodic carbonate, the jelly-like mass was pressed and dried, and the fat salt dissolved out with absolute alcohol; the alcoholic solution, when cold, gelatinized; the gelatinous mass was pressed, dried, and dissolved in alcohol, and filtered: this salt was not analyzed. Preparation of the Silver-salt.-The soda-salt was dissolved in hot water and precipitated by argentic nitrate; the precipitate was washed in the dark; the analysis of this salt yielded the following results : I. 2255 grm. gave '067 grm. Ag. II. 5088 grm. gave ·152 grm. Ag. 2 III. 6044 grm. gave 1.1572 grm. CO, and 4555 grm. H, 0= 3156 grm. C and ⚫05061 H. IV. 3267 grm. gave 634 grm. CO, and 257 grm. H,O=1729 C and 02855 H. The following are the calculated numbers for argentic palmitate: VOL. XVIII. 2 A Preparation of the Ether.-Dry hydrochloric acid gas was passed to saturation through a warm solution of the acid in absolute alcohol; the solution was then diluted with water, which caused the ether to separate as a yellowish oil, which, as it became cold, assumed the appearance of a waxy body; it was boiled with water, and afterwards agitated with a hot dilute solution of sodic carbonate; it was again dissolved in alcohol, and precipitated from this solution by water; it was then collected and dried; its analysis yielded the following results : I. 2197 grm. gave 6112 grm. of CO, and 25 grm. H, O=·1667 C and ⚫0278 H. 2 2 II. 204 grm. gave '567 grm. of CO, and ·233 grm. of H, O=15464 C and 02589 H. The following are the calculated numbers for ethylic palmitate, Preparation of the Baric Salt.-A hot alcoholic solution of the acid was saturated with ammonia in slight excess, and boiled with a solution of baric acetate; the precipitate falls as a white flocculent mass, which, when thoroughly washed, dried, and powdered, has the appearance of a glistening spongy powder. I. 276 grm. gave 0625 grm. of Ba O=23.64 per cent. I did not consider it necessary to make a carbon and hydrogen determi nation of the baric salt, or to examine any other salts of the acid, as the analysis of the acid, the silver-salt, and the ether, along with the determination of the baryta in the baric salt, I considered sufficiently indicated that the acid under examination was palmitic acid, although I could never obtain, even after fractional precipitation, a higher melting-point for the acid than 57° C. The difference in the melting-points of the acid mass before it was treated with alcohol, and the melting-point of the palmitic acid, indicated that at least one other acid was present, but in very minute quantity. I attempted to determine the nature of the acid of lower melting-point by exposing the residues obtained from the first three crystallizations of the hard acid to cold in a bath of sodic sulphate and hydrochloric acid, all the hard acid which crystallized out being rejected; the portion which remained fluid was saponified with potassic carbonate, and the solution of the potash soap was subjected to fractional precipitation by means of plumbic acetate; the second and smaller precipitate was collected and washed, and treated for some time at a moderate temperature with dilute sulphuric acid; this caused the separation of a reddish oily-looking liquid which was collected and dissolved in boiling alcohol; it was afterwards saponified with potassic carbonate, and the silver-salt prepared from that salt. I only obtained sufficient of the silver-salt from about 2 lbs. of oil to make one determination of the silver and one of the carbon and hydrogen, and from these determinations I did not obtain concordant results, and want of material compelled me to relinquish the further examination of the acid. Transactions. Presents received March 10, 1870. Bordeaux:-Académie Impériale des Sciences, Belles-Lettres et Arts. Actes. 3 série, 30° année 1868, 3me trimestre. 8vo. Paris 1868. The Academy. Lisbon:-Museu Nacional. Secção Zoologica. Catalogo das Collecções Ornithologicas. Junho de 1869. 8vo. Lisboa 1869. The Museum. Newcastle-on-Tyne :-Iron and Steel Institute. Transactions, Session 1869. (Nos. 1-3.) 8vo. Newcastle-on-Tyne 1869. The Secretary. Paris: Ecole des Mines. Annales des Mines. 2, 3, 4 livraisons de 1869. 8vo. Paris. The School. Ecole Normale Supérieure. Annales Scientifiques, par L. Pasteur. The School. |