Muffle furnaces are suitable for fine ores which are liable to decrepitate or sinter.
(a) Heating chamber fixed and forming part of furnace= muffle furnaces.
The " muffle," a graphite cylinder 6 in.
The precipitate is collected in a filter-press, and then roasted in muffle furnaces with nitre, borax and sodium carbonate.
high, and heated either in a muffle or in a crucible furnace at a gradually increasing heat for forty or fifty minutes.
Types of muffle furnaces are figured in the article Annealing, Hardening And Tempering.
The door of the muffle is then opened and the current of air which is drawn over the scorifier rapidly oxidizes the lead, while the melted litharge gradually closes over the metal.
In the .scorification method the ore is mixed in the scorifier (a shallow dish of burned clay) with from ten to twenty times its weight of granulated metallic lead (test lead) and a little borax glass, and heated in a muffle, the front of which is at first closed.
Chaplet has patented a muffle or tube furnace, similar in principle, for use on a larger scale, with a number of electrodes placed above and below the muffle-tube.
In consequence the fire-gases, when arriving there by the chimney shaft (a), have already a good upward draught, and when circulatung round the muffle are at a lower pressure than the gases within the muffle, so that in case of any cracks being formed, no hydrochloric acid escapes into the fire-flues, but vice versa.
These are known as muffle or chamber furnaces; and by supposing the crucibles or retorts to represent similar chambers of only temporary duration, the ordinary pot melting air furnaces, and those for the reduction of zinc ores or the manufacture of coal gas, may be included in the same category.
Metallurgical furnaces of the first class are termed crucible, muffle or retort furnaces, and of the second shaft and reverberatory furnaces.
It is, therefore, decidedly preferable to employ " muffle-furnaces " in which the heating is performed from without, the fire-gases passing first over the arch and then under the bottom of the muffle.
They should also purchase floor mats to muffle the sound of weights being dropped.
The scorifier is taken from the muffle in a pair of tongs and the contents poured into a mould, the lead forming a button in the bottom while the slag floats on top. When cold, the contents of the mould are taken out and the lead button hammered into the form of a cube, the slag, which is glassy and brittle, separating readily from the metal, which is then ready for cupellation.
It is not easy to keep the muffles permanently tight, and as soon as any leakages occur, either hydrochloric acid must escape into the fire-flue, or some fire-gases must enter into the muffle.
below the top of the muffle.
The process is effected either in heaps, stalls, shaft furnaces, reverberatory furnaces or muffle furnaces.
The sample may be heated up to about 800°C using a small muffle furnace while the platen is mounted on a water-cooled loading arm.
muffle the cry of pain.
muffle furnace while the platen is mounted on a water-cooled loading arm.
muffle material gives little indication of its features.
truncated cone, the broad end springing from the muffle Figure 4a.
WALLABY, a native name, used in literature for any member of a section of the zoological genus Macropus, with naked muffle, frequenting forests and dense scrubs.
If hot air is introduced into the kiln, the additional heat developed by the oxidation of the zinc and the sulphur is sufficient to keep up a part of the reaction; but for the complete expulsion of the sulphur an externally-fired muffle through which the ore is passed is found to be essential.
These do not hunt in packs, but will sometimes singly attack a bullock; they and the wolves make havoc among sheep. A favourite feat of the boldest of the young men of southern Afghanistan is to enter the hyena's den, single-handed, muffle and tie him.
The dry method consists in an oxidizing roasting of the ores, and a subsequent chloridizing roasting with either common salt or Abraumsalz in reverberatory or muffle furnaces.
In modern practice degreased bones (see Gelatin), or bone-ash which has lost its virtue as a filtering medium, &c., or a mineral phosphate is treated with sufficient sulphuric acid to precipitate all the calcium, the calcium sulphate filtered off, and the filtrate concentrated, mixed with charcoal, coke or sawdust and dried in a muffle furnace.
These burners, or modifications of them, have also been applied to muffle furnaces, which are convenient when only a few assays have to be made - the furnace being a mere clay shell and soon brought to a working temperature; but the fuel is too expensive to allow of their being used habitually or on a large scale.
They commonly take the form of a truncated cone, the broad end springing from the muffle Figure 4a.
For instance, the Tennessee Spirit Mike is said to muffle human conversation and ambient noises while zeroing in on spirit voices.
The word usage examples above have been gathered from various sources to reflect current and historial usage. They do not represent the opinions of YourDictionary.com.