SCIENTIFIC INTELLIGENCE. I. PHYSICS. 1. On the passage of radiant heat through polished, rough, and smoked rock-salt, and on the diffusion of rays of heat.-H. KNOBLAUCH has contributed a very elaborate and valuable investigation of the transmission of radiant heat through rock-salt. We give the results in the author's own words, referring the reader for details of apparatus and methods to the original memoir. I. (1.) Clear chemically pure rock-salt permits rays of heat of all kinds to pass through it in equal proportion, whether the difference between the rays depends upon the fact a. that they are diffusely reflected from different bodies, or b. transmitted through different diathermanous bodies, or c. radiated from different sources of heat. (2.) In the case of this absorption, equally exercised upon all elementary rays, it is proved that in the solar spectrum of a rock-salt prism the maximum of heat falls in the dark space beyond the red; within the visible portion of the spectrum the distribution of heat is the same in the case of prisms of rock-salt and flint glass. II. (1.) The heat rays of the sun pass through rough as well as cloudy rock-salt in a less proportion than those of an Argand lamp, and these last, as a rule, in a less proportion than the rays of a source of heat at 100° C. An increase of roughness diminishes the transmission of every kind of heat but affects solar heat most, that of a lamp less, and that of a dark source least of all. (2.) Independently of the elective absorption exerted by the substance, the rough surface of unpolished glasses exercises an influence corresponding to that of the internal cloudiness in milky glasses. (3.) These phenomena can not be referred (with Forbes) to an absorption which affects qualitatively different rays of heat unequally, nor (with Melloni) to an unequal dispersion in the rough and cloudy media depending on the heat-color, by which the rays are more or less deviated from the thermoscope. Neither is the roughness of the surface in itself, nor the direction of the rays proceeding from a single point the determining condition. (4.) The diffuse heat arising from radiation through rough or cloudy screens or reflection from rough surfaces radiates more abundantly through diffusing screens according as (a) the rays are more diffuse, (b) in comparison with parallel rays, as the screens are more diffusive. (5.) In fact the really determining condition of the passage through these screens is whether the incident rays are parallel, or more or less variously radiated from a greater or less number of points. (6.) Hence, for one and the same source of heat, the ratio of transmission in question (in spite of a constant quantity of heat falling directly upon the plates) diminishes with the distance of the source, and the more rapidly the more diffusive the screen. (7.) It is possible, by a proper arrangement of the experiments, to cause the more abundant passage of rays of heat from a source at 100° C. in comparison with those from the lamp, cited in (1.), to disap pear, and even, conversely, to bring about a more abundant transmission of the heat of the lamp. III. (1.) In the passage of radiant heat through rock-salt covered with soot an elective absorption (suspected by Melloni) takes place without diffusion. A diffusive action (supposed by Forbes) never takes place in consequence of the rough surface of the layer of soot, but sometimes in consequence of a tarnishing of the rock-salt plate in the process of cov ering with soot. (2.) In the case of transmission through thin layers of metal laid upon glass the first process takes place without the last. (3.) The presence of an elective absorption exerted during transmission is most certainly recognized by determining whether the heat before and after its passage through the substance in question retains unchanged or varies its capacity to pass through other (clear) diathermanous bodies with a smooth surface. (4.) A diffusive action is best tested by either of the following methods. a. If solar heat be allowed to pass through the screen in question, and the transinitted be compared with the direct rays, either both groups of rays exhibit an equal power of transmission through colorless rock-salt, or else the first passes more freely than the second group. In this last case the plate investigated is diffusive. b. When, of two groups of rays of the same thermic color, one of which consists of parallel and the other of diffusive rays, the latter passes most easily through the substance tested, this substance is diffusive. In this process a method is pointed out for the comparison with each other of different degrees of diffusion within very wide limits. IV. (1.) a. By diminishing the angle which the rays of heat form with an unpolished or cloudy plate the diffusion exerted upon them is in general increased. This increase, with the change in inclination, in the first place becomes larger with the generally diffusive property of the screen, but then again grows less to such a degree that in very rough and sufficiently cloudy plates, just as in the case of clear ones no difference can be detected in the behavior of rays which are transmitted at different angles of inclination. b. A diffusion produced by reflection from rough surfaces diminishes, on the contrary, for the more obliquely incident rays, and passes finally into regular reflection. (2.) Between the smooth and the two-sided rough surface there are circumstances, in consequence of which, independently of every process in the interior of the substance, the simple mechanical quality of the surface produces a "coloration" of the transmitted heat. (3.) It follows, therefore, that in the case of the rough and cloudy media in question, a distinction must be made between the action of the diffusion, which is always present, and that of the elective absorption which sometimes occurs. (4.) Fused common salt produced a diffusion but no heat-coloration. (5.) Another piece of rock salt was found to be chemically and mechanically impure, and exercised both a diffusive action and an elective absorption. Circumstances of this kind explain the varying observations made in different experiments with rock-salt.-Pogg. Ann., cxx, 177. W. G. II. CHEMISTRY. 1. On a cyanid of phosphorus.-HÜBNER and WEHRHAUE have described a tercyanid of phosphorus obtained by the following process. Perfectly dry cyanid of silver is heated in a glass tube with an equivalent quantity of terchlorid of phosphorus diluted with chloroform. The double decomposition requires a temperature of 120° C. to 140° C. for several hours. The chloroform is distilled off in a current of carbonic acid gas and the cyanid of phosphorus sublimed into the neck of the retort. Tercyanid of phosphorus forms long brilliant snow-white crystals. When gently heated they take fire in the air and burn with a bright light. Water decomposes the cyanid with violence, forming phosphorous and cyanhydric acids. The crystals melt and volatilize at about 190° C. Analysis proved that the constitution of the cyanid of phosphorus is PCy; the authors propose to study the products of its decomposition.Ann. der Chemie und Pharm., cxxviii, 254, Nov. 1863. W. G. 2. On Indium.-REICH and RICHTER have given some further details of the new metallic element, Indium, discovered by them in the Freiburg blendes. Indium gives in the spectroscope two blue lines, of which the brighter stands at 98, the fainter at 135, of a scale on which the sodium line stands at 38, and the blue strontium line at 93. A compound of indium colors the flame of Bunsen's burner violet, so that the presence of the metal may be detected without the spectroscope. The metal as obtained by reducing the oxyd before the blowpipe on charcoal with soda is soft and ductile, leaving on paper a streak which is brighter than that of lead and somewhat like that of tin. The metal dissolves in chlorhydric acid with evolution of gas, and the solution gives the blue line with great intensity. The hydrated oxyd precipitated by ammonia is white and shiny tartaric acid prevents its precipitation by ammonia, but sulphid of ammonium produces in this solution a voluminous white precipitate. Potash behaves like ammonia; carbonate of soda precipitates a white crystalline carbonate. The oxyd ignited in a current of hydrogen gave no water and remained unchanged. Heated with carbon in a current of chlorine the oxyd yields a very volatile chlorid condensing in colorless crystalline leaves with the lustre of mother of pearl. This chlo rid deliquesces readily, and on drying is partially decomposed. The chlorid gives the blue line in the spectroscope with great intensity, but in this case the duration of the line is very short. It is better to heat the oxyd in a platinum spoon with a little chlorhydric acid, when the blue line is rather less brilliant but lasts longer. A solution of the metal in chlorhydric acid gives with ammonia and sulphid of ammonium a grayish brown precipitate, but it is possible that the color may arise from impurities. The separation of iron from indium is difficult. The chlorid gave with ferrocyanid of potassium a white precipitate, with a shade of blue from the presence of iron, ferrideyanid gave no precipitate, sulphocyanid of potassium a pale red, owing to the presence of iron. The oxyd gives no blue color before the blowpipe with cobalt solution, and after ignition dissolves slowly but completely in chlorhydric acid. The authors satisfied themselves that indium occurs only in the Freiberg zincblende, and not in the arsenkies and schwefelkies.-Journ. für prakt. Chemie, Band 90, 172. W. G. AM. JÕUR. SCI.—Second Series, VOL. XXXVII, No. 110.—MARCH, 1864. III. MINERALOGY AND GEOLOGY. 1. Eusynchite and Dechenite.-In an extended investigation on Vanadium, C. CZUDNOWICZ reviews the analyses of vanadinite, dechenite, aræoxene and eusynchite. He shows, that the method used by Tschermak for the indirect determination of vanadic acid, in the rhombic vanadinite from Kappel in Carinthia, is incorrect, and the conclusion that the mineral was a simple vanadate of lead, PbV, is an assumption not justified by the facts: the only datum for this, being a single determination of the per-centage of lead. Czudnowicz gives the following new analyses of eusynchite : From these results it appears that eusynchite is a ter-basic vanadate of lead and zinc, with the formula (Pb, Zn)3V. Czudnowicz calls attention to the analogy between eusynchite, aræoxene and dechenite, and suggests that the latter may contain zinc, the presence of which might have been overlooked, as was the case in Nessler's analysis of eusynchite.-(Pogg. Ann., cxx, 17.) [In a note to Nessler's analysis of eusynchite, published in the 4th Supplement to Dana's Mineralogy (this Journal, [2], xxiv, 116, July 1857), I stated that, on qualitative analysis of this mineral, I had found it to contain zinc, and attention was also called to its remarkable resemblance to dechenite. This statement is now confirmed by the analyses of Czudnowicz, although he has overlooked my observations on eusynchite, as also the fact that in the same article I pointed out the existence of zinc in dechenite, and suggested the probability that dechenite and aræoxene were identical. About the time my note was published, Bergemann gave the following analysis of aræoxene in Leonhard and Bronn's Jahrbuch für Mineralogie (1857, p. 397): Bergemann mentions that aræoxene and dechenite occur together at Dahn, in the Palatinate, but that dechenite may be distinguished from aræoxene by the color, the former being a beautiful red, while the latter is reddish-brown to deep brown. In the original analyses of dechenite by Bergemann, he found in the dark red crystalline variety, in two determinations, 52.92 and 53.72 p. c. of oxyd of lead, and in the yellowish variety 50-57 p. c. of oxyd of lead. In some specimens, he obtained on charcoal a reaction for arsenic, although, he says, the pure specimens contained no arsenic. It would seem then, that Bergemann considers aræoxene and dechenite distinct mineral species; he, however, gives us no new examination of dechenite, but merely re-asserts that dechenite is a neutral vanadate of lead. I have examined a specimen of dechenite obtained from Dr. Krantz in 1851, shortly after Krantz and Bergemann had described this species, and have found that it contains, not only zinc, but arsenic. The specimen has the appearance of being pure and unaltered; it is perfectly homogeneous, has a brownish-red color, is botryoidal It in form, and, under the lens, its structure appears crystalline. There is every probability that this specimen, which Dr. Krantz, the discoverer of the species, called dechenite, has the same composition. as aræoxene. is worthy of note, that the method used by Bergemann for the quantitative determination of vanadic acid, would not separate it from arsenic acid and oxyd of zinc, had such been present. Further, it is suggested by Czudnowicz, that the fact that Bergemann was unable to separate sulphuric acid from the so-called pure vanadic acid by heat, indicated the presence of a base with the vanadic acid, as it is well known, and fully established by the observations of Fritzsche and Schafarik, that there is no difficulty whatever in effecting this separation. It is also a somewhat singular coincidence that dechenite, if it be a neutral vanadate, should happen to have the same percentage of oxyd of lead as the terbasic vanadate aræoxene. It is further somewhat peculiar, if they are distinct species, that their specific gravity should be so nearly identical: dechenite having a density of 5.81, while that of aræoxene is 5.79. The same may be said of their hardness and the other physical characters, except a questionable difference in color. Any one reading v. Kobell's description of aræoxene' and Bergemann's original description of the physical characters of dechenite could hardly fail to conclude that they are the same mineral. To all this, adding the fact that Dr. Krantz, the discoverer of dechenite, considers the two minerals to be identical, and further, that a specimen of the so-called pure dechenite, received from Dr. Krantz, as early as 1851, proves to have all the characters of aræoxene, we think we may safely question the accuracy of Bergemann's results in his examination of dechenite. Czudnowicz calls especial attention to the circumstance that all the native vanadates thus far described, of which we have trustworthy analyses, are basic in their character.-G. J. B.] 2. Göthite from Lake Superior.-This mineral is found associated with hematite at the Jackson Iron Mountain, near Marquette, Lake Superior. Some of the specimens have the hyacinth red color which characterizes the variety of göthite called by the Germans "Rubinglimmer." It also occurs in acicular crystals of an almost velvet-black color and lustre, and it is occasionally found in distinct trimetric crystals. A determination of the water gave 10:47 p. c. G. J. B. 3. Szaibelyite. This new borate, described by Peters and already noticed briefly in this Journal,' has been further investigated by Stromeyer and Peters. It occurs disseminated through a gray granular limestone at Werksthal near Retzbanya. This limestone, treated with dilute nitric acid in the cold, gave a residue consisting of a crystalline powder, and also rounded kernels of the size of a lentil. These kernels are translucent, white on the exterior, and interiorly yellowish. Hardness, between 3 and 4. Stromeyer found the limestone to contain 16.6 of crystalline needles, and 148 of the rounded kernels. The specific gravity of the former was 27, of the latter 3.0. The air-dried mineral was constant in weight at 100° C. Analysis of the two varieties gave: |