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Germicidal value of thymol
402
CURRENT ToPIcs.
Absorption of Iodine by Solid Substances.
M. GUICI-I:',RDo
(Comptes rendus, cli, 236.)--Silica , both natural and calcined; alumina, calcined at 6oo°C.; magnesia, calcined at IO25°C.; and glucina all absorb iodine in quantities inversely proportionate to the degree of calcination. The differences in absorption are due to the shrinkages of the interspaces between the particles, and the cessation of absorption probably marks the disappearance of these interspaces and corresponds with the maximum density of the substance.
Chemical Standards for Iron Castings. Jott_x T. PORTER. (_~brier. Mach., xxxiii, 3 2 . ) - - T h i s article ~ill repay careful perusal. It m a y be summarized as below. Cast-iron treated as an alloy, and the effect of the various ingredients present in the n~etal, or used in making the required mixtures. The physical properties of the metal and its behavior at different temperatures. The classification of castings, and the chemical composition of iron castings as used for various purposes; with a suggestion as to the best mixture to use for numerous purposes to which iron castings are put.
Design of Centrifugal P u m p s . A. ~ORSODY. (A~11.CT'. Mach., xxxiii, 39.) This paper deals w~ith the losses occurring in centrifugal pumps, their analysis and steps taken to reduce them. T h e principal losses in centrifugal pumps are well recognized, and by careful aI~alysis they can be separated and the design regulated so as to produce the highest efficiency. }?or high heads, requiring high peripheral speeds, a diffusion-ring is employed, constituting a turbine pump. The diffusion-ring contains passages which split up the water from the impeller into streams, gradually transforming its velocity into pressure and reducing the whirlpool losses in the casing. ~ special construction described for surrounding the impeller with air, instead of water, so as to cut down the side friction, which is one of the principal losses in a centrifugal pump. These principal losses are: I. Side friction of impellers called the rotor friction. 2. Hydraulic friction losses in the stationary parts of the pump. 3. Losses in the whirlpool chamber and losses at the periphery of the impeller. Germicidal Value of T h y m o l . E . W . SCtKMIDT. cZeit. Phys. Thymol has been used as an antiseptic and disinfectant especially in physiological experiments oil digestion. The author examines its value in this direction. ]Experiments were made with albumin, peptone, fibrin, organisms and enzwnes in t h e presence of saturated thymol water. All e x p e r i m e n t s w e r e made at a temperature of 25°C. which is the most favorable to putrefac-
Chem., lxvii, 412.)
CURRENT TOPICS.
403
tive organisms. No difference could be found in the putrefactive actions whether the experiment was made ence or absence of thymol. Hence the conclusion is has no power to inhibit bacterial growth and is of no antiseptic or disinfectant.
digestive or in the presthat thymol value as an
Action of Metallic Contacts on a Filings Coherer. B. SZILARD. (Comptes rendus, cl, I 6 7 o . ) - - T h e author finds that a filings coherer is very much more sensitive when the end of the coherer (which is earthed in the usual arrangement) is connected to one terminal of an alternating-current system, the other alternatingcurrent terminal being connected to earth, H e finds that a coherer connected in this manner is affected when a meta!lic rod set up as sending antenna, is simply touched by a piece of metal held in the hand. This action is obtained over I5O cm. The contact between the two pieces of metal must be very light and between ipoints. The metals brought into contact may be the same or may differ. The maximum distance at which the effect is obtained depends upon the metals used. Carbonization of Rubber by Mercury Vapor. W. VON BOLTON. (Zeit. Elektrochem., xvi, 6 6 7 . ) - - M e r c u r y vapor decomposes volatile hydrocarbons, chloroform, carbon tetrachloride, carbon bisulphide, carbon dioxide and hydrogen sulphide with separation of carbon or sulphur. This reaction does not occur with liquid mercury, even at boiling temperature, but only by the monatomic vapor. Amalgams seem to produce the vapor more rapidly than pure metal, probably on account of their larger surface, but the action is noticeable in presence of mercury heated to Ioo°C. for about three weeks. Sulphur accelerates the action, selenium and tellurium retard it. Traces of moisture are requisite. If mercury vapor attacks pure non-vulcanized rubber, no carbon is separated but the rubber becomes hard and brittle and traces of mercury can b e found in it. The carbon separated in ordinary experiments is found to contain small' m*icroscopic crystals of diamond. The
Inventor
of the
Black-Ash
Furnace.
W.
RAMSAY.
(Chem. News, cii, 6 9 . ) - I n the correspondence of Dr. Joseph Black
a letter to him from a Mr. George Golder was found, bearing the date of March 19, I782, advising Dr. Black t h a t M r . Golder was .sending him a sample of ashes made by Messrs. Collison and Co., London, with a copy of Collison's specification for making mineral and vegetable alkali, by the use of a reverberatory furnace. Dr. Black examined the ash and found it about 5° per cent. stronger than the best Alicant barilla, and about seven times the s t r e n g t h of "kelp. The patent granted to Le Blanc for the process of manufacturing sodium carbonate and sodium hydrate was dated Sept. 23, i79~ , and is therefore nine years later than Collison's patent.
CURRENT ToPIcs.
Absorption of Iodine by Solid Substances.
M. GUICI-I:',RDo
(Comptes rendus, cli, 236.)--Silica , both natural and calcined; alumina, calcined at 6oo°C.; magnesia, calcined at IO25°C.; and glucina all absorb iodine in quantities inversely proportionate to the degree of calcination. The differences in absorption are due to the shrinkages of the interspaces between the particles, and the cessation of absorption probably marks the disappearance of these interspaces and corresponds with the maximum density of the substance.
Chemical Standards for Iron Castings. Jott_x T. PORTER. (_~brier. Mach., xxxiii, 3 2 . ) - - T h i s article ~ill repay careful perusal. It m a y be summarized as below. Cast-iron treated as an alloy, and the effect of the various ingredients present in the n~etal, or used in making the required mixtures. The physical properties of the metal and its behavior at different temperatures. The classification of castings, and the chemical composition of iron castings as used for various purposes; with a suggestion as to the best mixture to use for numerous purposes to which iron castings are put.
Design of Centrifugal P u m p s . A. ~ORSODY. (A~11.CT'. Mach., xxxiii, 39.) This paper deals w~ith the losses occurring in centrifugal pumps, their analysis and steps taken to reduce them. T h e principal losses in centrifugal pumps are well recognized, and by careful aI~alysis they can be separated and the design regulated so as to produce the highest efficiency. }?or high heads, requiring high peripheral speeds, a diffusion-ring is employed, constituting a turbine pump. The diffusion-ring contains passages which split up the water from the impeller into streams, gradually transforming its velocity into pressure and reducing the whirlpool losses in the casing. ~ special construction described for surrounding the impeller with air, instead of water, so as to cut down the side friction, which is one of the principal losses in a centrifugal pump. These principal losses are: I. Side friction of impellers called the rotor friction. 2. Hydraulic friction losses in the stationary parts of the pump. 3. Losses in the whirlpool chamber and losses at the periphery of the impeller. Germicidal Value of T h y m o l . E . W . SCtKMIDT. cZeit. Phys. Thymol has been used as an antiseptic and disinfectant especially in physiological experiments oil digestion. The author examines its value in this direction. ]Experiments were made with albumin, peptone, fibrin, organisms and enzwnes in t h e presence of saturated thymol water. All e x p e r i m e n t s w e r e made at a temperature of 25°C. which is the most favorable to putrefac-
Chem., lxvii, 412.)
CURRENT TOPICS.
403
tive organisms. No difference could be found in the putrefactive actions whether the experiment was made ence or absence of thymol. Hence the conclusion is has no power to inhibit bacterial growth and is of no antiseptic or disinfectant.
digestive or in the presthat thymol value as an
Action of Metallic Contacts on a Filings Coherer. B. SZILARD. (Comptes rendus, cl, I 6 7 o . ) - - T h e author finds that a filings coherer is very much more sensitive when the end of the coherer (which is earthed in the usual arrangement) is connected to one terminal of an alternating-current system, the other alternatingcurrent terminal being connected to earth, H e finds that a coherer connected in this manner is affected when a meta!lic rod set up as sending antenna, is simply touched by a piece of metal held in the hand. This action is obtained over I5O cm. The contact between the two pieces of metal must be very light and between ipoints. The metals brought into contact may be the same or may differ. The maximum distance at which the effect is obtained depends upon the metals used. Carbonization of Rubber by Mercury Vapor. W. VON BOLTON. (Zeit. Elektrochem., xvi, 6 6 7 . ) - - M e r c u r y vapor decomposes volatile hydrocarbons, chloroform, carbon tetrachloride, carbon bisulphide, carbon dioxide and hydrogen sulphide with separation of carbon or sulphur. This reaction does not occur with liquid mercury, even at boiling temperature, but only by the monatomic vapor. Amalgams seem to produce the vapor more rapidly than pure metal, probably on account of their larger surface, but the action is noticeable in presence of mercury heated to Ioo°C. for about three weeks. Sulphur accelerates the action, selenium and tellurium retard it. Traces of moisture are requisite. If mercury vapor attacks pure non-vulcanized rubber, no carbon is separated but the rubber becomes hard and brittle and traces of mercury can b e found in it. The carbon separated in ordinary experiments is found to contain small' m*icroscopic crystals of diamond. The
Inventor
of the
Black-Ash
Furnace.
W.
RAMSAY.
(Chem. News, cii, 6 9 . ) - I n the correspondence of Dr. Joseph Black
a letter to him from a Mr. George Golder was found, bearing the date of March 19, I782, advising Dr. Black t h a t M r . Golder was .sending him a sample of ashes made by Messrs. Collison and Co., London, with a copy of Collison's specification for making mineral and vegetable alkali, by the use of a reverberatory furnace. Dr. Black examined the ash and found it about 5° per cent. stronger than the best Alicant barilla, and about seven times the s t r e n g t h of "kelp. The patent granted to Le Blanc for the process of manufacturing sodium carbonate and sodium hydrate was dated Sept. 23, i79~ , and is therefore nine years later than Collison's patent.