Chemical news and Journal of physical science: Chemical news and Journal of physical science

Crookes, William

Bibliografische Daten

Zeitschrift

Persistenter Identifier:: 1602495396786

Titel:: Jahreshefte des Vereins für Vaterländische Naturkunde in Württemberg : zugl. Jahrbuch d. Staatlichen Museums für Naturkunde in Stuttgart

Erscheinungsort:: Stuttgart

Erscheinungsverlauf:: 18XX

Strukturtyp:: Zeitschrift

Sammlung:: Gesellschaft für Naturkunde in Württemberg e.V.

Lizenz:: https://creativecommons.org/publicdomain/mark/1.0/deed.de

Band

Persistenter Identifier:: 1602495396786_38_1882

DOI:

Titel:: Jahreshefte des Vereins für Vaterländische Naturkunde in Württemberg : zugl. Jahrbuch d. Staatlichen Museums für Naturkunde in Stuttgart

Herausgeber:: Fehling, Hermann Christian von; Fraas, Oscar; Krauß, Ferdinand von; Zech, Paul

Jahrgang/Band:: Bd. 38, 1882

Erscheinungsjahr:: 1882

Sprache:: deutsch

Strukturtyp:: Band

Standort:: Universitätsbibliothek Stuttgart

Signatur:: XIX965/8

Lizenz:: https://creativecommons.org/publicdomain/mark/1.0/deed.de

Sammlung:: Gesellschaft für Naturkunde in Württemberg e.V.

Teil

Titel:: II. Vorträge

Strukturtyp:: Teil

Cugion Neve) New and Modified Specific Gravity Apparatus. 85 | is in any way inferior in accuracy to the original form THE CHEMICAL NEWS, goed Some x The accompanying figure (1) gives the form of the tube. It is made from a test-tube 15 m.m. in diameter, the Vor. XLVIL. No. 1213. length of the wide part is 115 m.m., and the distance from the shoulder to the bend is 40 m.m. to allow of the total immersion of the body of the tube in the water of the constant temperature bath. The capillary tubes have ON THE EXAMINATION OF AMERICAN CHEESES. By A. B. GRIFFITHS, F.C.S,, Member of the Liverpool Association of Science and Arts, Medallist in Chemistry and Botany, &c. Tae author has recently submitted to careful analysis four samples of American cheese purchased in London, and handed to him for analysis. The results are as follows : — 1, Water... .., 2249 Caseine . Fat ,. . Ash .. IV. 31°81 36°10 28°68 3°40 99°66 9990 099'88 g9'99 The author also made a separate analysis of the rind in each case, and in samples Nos. I, and IV. a small amount of arsenic was found, This was probably applied to the external surfaces of the cheeses to prevent the attacks of inseds, &c.,—a practice which is dangerous to the con- sumer, and ought to be prohibited by law, I also ex- amined microscopically each of the samples of cheese for vegetable fibres, &c., and starch granules, but found no traces. "a London, January 31st, 1883. SUPERSATURATION. By SPENCER UMFREVILLE PICKERING, B.A. (Oxon.) SUPERSATURATION is not, I believe, generally supposed to take place in a solution when any of the solid substance is present : I had occasion, however, to notice an instance in which it took place under these c'rcumstances to a marked extent. A boiling saturated solution of copper sulphate had been left to filter undisturbed into an open beaker. When a'most cold a considerable crop of crystals had formed on the bottom and sides of the beaker and on a glass rod in it; but on moving this rod a sudden deposition of very small crystals of the sulphate took place, amounting to about twice the quantity of those which had separated slowly, and which could not have weighed less than [O00 grammes NEW AND MODIFIED SPECIFIC GRAVITY APPARATUS. By W. W. NICOL, [N the Chemical Society’s Yournal for 1873, p. 577, occurs a description of the now well-known Sprengel tubes for the determination of the specific gravity of liquids. The form there described has, however, certain disadvantages : it is by no means easy for an’ inexperienced glass-blower to make such a tube, and when made it is difficult to fill without including air bubbles, or entailing some loss of liquid. After I had used the above form for some time, [ modified it as follows, and have used this modified form n many hundred experiments without observing that it Ce AES 2k Fl G.I. © an external diameter of about 25 m.m.,and a bore of 0'5 to o'7 m.m. The total length from a to B is 180 m.m., and the mark is at ¢. Such a tube weighs 15 to 16 grms., and holds 13 to 15 c.c., and is capable of giving results with a maximum error of 4-0'c0002. The above form of tube can of course only be used to determine the specific gravity of liquids, but the following modification adapts it for the determination of that of solids soluble in water (Figure 2) :—The only differences Lo TE —— A C—————— = — 0 o le. 2 tom the foregoing are that the wide capillary starts from he upper part of the body of the tube, and that half way own a wide open tube is joined in at right angles. The 1se of this apparatus is as follows: The salt (in fine sowder) whose specific gravity is to be determined, is shaken in by p. The outer edge of bis then sortened in he blowpipe flame, closed, and rounded by gently blowing n at B. The whole is then weighed, partially filled with saraffin oil, the air exhausted by B until on shaking up the yowdered salt no air bubbles make their appearance, then illed up with paraffin, and, after attaining the tempera- cure of the bath, again weighed. Then washcd out with vater and alcohol, dried, and weighed—first e:npty. then

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