Hydrometer

“ The hydrometer constructed by Dicas of Liverpool is provided with a sliding scale which can be adjusted for different temperatures, and which also indicates the contraction in volume incident on bringing the spirit to proof strength. It is provided with thirty-six different weights which, with the ten divisions on the stem, form a scale from 0 to 370. The employment of so many weights renders the instrument ill-adapted for practical work where speed is an object. ”

“ A piece of wood cut from the spoke of an old wheel was loaded at one end with lead, so as to make it stand upright. It was immersed in rain-water, and the water-level on it marked 1,000. By means of a Baumæ's hydrometer the level of 900 was found, and distances, equal to the distance between the two marks, laid off above and below. Much to the boy's surprise, the hydrometer thus graduated would by no means coincide with his Fig. 2.—Hydrometer. ”

“ Testing With Hydrometer The estimation of the gravity of the boiling pulp by the use of a hydrometer is not in very general use, and it has been stated by some scientific men that a hydrometer is no good for tomato pulp or catsup except where the sample on which the test is made is previously filtered so as to get a clear liquid. A test which involves filtering, is, in my opinion, entirely unsuited for everyday use on the cooking platform. ”

“ Charles’s balance areometer is similar to Nicholson’s hydrometer, except that the lower basin admits of inversion, thus enabling the instrument to be employed for solids lighter than water, the inverted basin serving the same purpose as the pointed screw in Atkins’s modification of the instrument. ”

“ In every case in which the supersalted water is discharged from the boiler in a continuous stream, a hydrometer or salt gauge of some convenient construction should be applied to the boiler, so that the density of the water may at all times be visible, and immediate notice be given of any interruption of the operation. ”

“ In the fabrication of hydrometers more special work comes in. The transparency of the material is not here an essential feature, although it is utilized and the graduation placed inside of the tube. The quality which renders glass particularly available for this service is its indifference to chemical reagents and its constant weight. The principle upon which hydrometers are constructed is familiar to all. In order that an object may float, it must displace its own weight of the supporting fluid. ”

“ The smaller tube is to form the hydrometer proper, while the larger one is to serve as a containing vessel in which the liquid to be tested is placed. The large tube should be mounted in a vertical position, by placing it in a hole bored in a small block of wood, or a suitable metal or wooden frame may be made that will accommodate one or more tubes. ”

“ The first important improvement in the hydrometer after its reinvention by Boyle was introduced by G. D. Fahrenheit, who adopted the second mode of construction above referred to, arranging his instrument so as always to displace the same volume of liquid, its weight being varied accordingly. Instead of a scale, only a single mark is placed upon the stem, which is very slender, and bears at the top a small scale pan into which weights are placed until the instrument sinks to the mark upon its stem. ”

“ The plan commonly adopted to obviate the necessity of inconveniently long stems is to construct a number of hydrometers as nearly alike as may be, but to load them differently, so that the scale-divisions at the bottom of the stem of one hydrometer just overlap those at the top of the stem of the preceding. ”

“ For the sake of uniformity, it is urgently to be desired that all manufacturers who use the hydrometer to estimate the content of a liquid in ammonia, potash, soda, hydrochloric, sulphuric, nitric acids, etc., should employ simple specific gravities. ”

“ The hydrometer will determine the strength accurately and beyond all question, the dealer therefore should make his purchases, estimating the strength by the specific gravity either in decimals or degrees. ”

“ The specific gravity of fluids is also taken by the instrument called a hydrometer or alcometer. Such instruments are much used for ascertaining the specific gravity of spirituous and other liquors, as an indication of their strength. If the solid body to be tested is lighter than water, it must be attached to some heavy substance to cause it to sink. Its specific gravity is then calculated by dividing its weight in the air by the sum of the weights of the attached body both in air and in water, first subtracting from this sum the weight of the two bodies together in the water. ”

“ The ‘Preuve d’Holland’ test, of the French, or the ‘BEAD,’ is still frequently employed by persons unacquainted with the use of the hydrometer. It consists in shaking the spirit in a phial, and observing the size, number, and duration of the bubbles or beads, as they are called. The larger and more numerous these are, and the more rapidly they break and disappear, the stronger the spirit is presumed to be. This method is unreliable, as the presence of sugar or acid, even in minute quantities, will sometimes give to a weak sample the appearance of one many degrees stronger. ”

“ The various methods of graduation ought all to give place to one showing a simple statement of the sp. g.
The method of determining sp. g. with the hydrometer is obviously inapplicable to the case of solids, and in the case of liquids it should not be used where exact figures are required. ”

“ It is impossible, says he, that the hydroscopium could be the level or chorobates of Vitruvius, for the lines on the latter were perpendicular to the horizon, whereas the lines on the former were parallel to it. The hydroscopium was undoubtedly a hydrometer of the simplest construction. The tube may be made of copper, and open at the top ”

“ The hydrometer is said by Synesius Cyreneus in his fifth letter to have been invented by Hypatia at Alexandria,1 but appears to have been neglected until it was reinvented by Robert Boyle, whose “New Essay Instrument,” as described in the Phil. ”

“ This weight will exceed w in consequence of the water displaced by the solid, and the weight of the water thus displaced will be W1−w, which is therefore the weight of a volume of water equal to that of the solid. Hence, since the weight of the solid itself is W−w, its density must be (W−w) / (w1−w) .
The above example illustrates how Nicholson’s or Fahrenheit’s hydrometer may be employed as a weighing machine for small weights. ”

“ Water which has stood for some time in a warm room becomes less in volume, or contracts, if it is taken into a cool place; while its volume increases, or it expands, if it is made hot. The same thing is true of quicksilver, of spirit, and of liquids in general. A thermometer is simply a small flask—the bulb—with a long and narrow neck—the tube—filled with as much mercury or spirit as will rise a short distance into the neck. If the liquid in the bulb is warmed, its volume is increased and it overflows into the tube, increasing the height of the column of liquid in the tube. ”

“ Experiments conducted in several of the larger cities of England with various types of water meters—which are really motors on a small scale—have proved the practicability of obtaining a source of constant power from what may be termed the ebb and the flow of pressure within the pipes of a water supply system.
At every hour of the day there is a marked variation in the quantity of water that is being drawn away by consumers, and consequently a rise and fall in the degree of pressure recorded by the meter. ”

“ When the thermometer is drawn up from deep water, the height at which the lower end of the index stands in each tube indicates the limit to which the index has been driven by the mercury, the extreme of heat or cold to which the instrument has been exposed. Unfortunately, the accuracy of the ordinary Six's thermometer cannot be depended upon beyond a very limited depth, for the glass bulb which contains the expanding fluid yields to the pressure of the water, and compressing the contained fluid, gives an indication higher than is due to temperature alone. ”

“ At all other elevations a mean error of 100 feet is on the average what is to be expected in ordinary cases. For the elevation of great mountain masses, and continuously elevated areas, I conceive that the results are as good as barometrical ones; for the general purposes of botanical geography, the boiling-point thermometer supersedes the barometer in point of practical utility, for under every advantage, the transport of a glass tube full of mercury, nearly three feet long, and cased in metal, is a great drawback to the unrestrained motion of the traveller. ”

“ The telescopic movement, and the mode of supporting the thermometer, enable the observer always to keep the bulb near the water, and the double tube gives all the protection required to obtain a steady boiling-point. Some boiling-point thermometers are constructed with their scales altogether exposed to the air, which may be very cold, and consequently may contract to some extent the thread of mercury outside the boiler. The steam, having the same temperature as the boiling water, keeps the tube, throughout nearly its whole length, at the same degree of heat, in the apparatus described. ”

“ It was found, however, that, by the process known to chemists as osmosis, this light gas in time partially escaped, and the remainder became mixed with air, the consequence being that the graduations were no longer correct. They are more durable as at present constructed. The liquid rises and falls in the tube with the variations of atmospheric pressure and temperature acting together. If the pressure were constant, the confined air would expand and contract for temperature only, and the instrument would act as a thermometer. ”

“ HYPSOMETER (Gr. ὕψος, height, μέτρον, a measure) , an instrument for measuring heights which employs the principles that the boiling-point of a liquid is lowered by diminishing the pressure, and that the barometric pressure varies with the height of the point of observation. The instrument consists of a cylindrical vessel in which the liquid, usually water, is boiled, surmounted by a jacketed column, in the outer partitions of which the vapour circulates, while in the central one a thermometer is placed. ”

“ The water then drops into the end of the tilt which happens to be uppermost, and when quite full it falls over, throwing the water into the globe, S, from which it flows away by the waste pipe. In this way an imperfect vacuum is produced in the globe, quite sufficient to produce a draught in the small tube of the syphon, or the long leg; and the whole contents of the reservoir, G, immediately run off, and the spiral springs, b b, elevate the reservoir to its original position. To produce this action, a quarter of an inch of rain must have fallen. The registration is easily understood. ”

“ The water-meter which is the subject of the patent consists of two parallel horizontal cylinders, each traversed by two pistons, connected together by a connecting-rod of such length that when one piston is at one end of the cylinder the other is at a sufficient distance from the other end, to leave the requisite space to be filled with the quantity of water to be measured at each stroke. ”

“ When the moisture is close to saturation two or three successive determinations may be necessary for a satisfactory result. When the humidity is very low the difference between the dry- and the wet-bulb reading of several determinations may be considerable. In this case, too, the observer must use his judgment. A mean of several determinations is a fairly safe record.
When the water in the cup of the Mason hygrometer is frozen, care should be used in making the reading. If the upper end of the wick is dry—sometimes this is the case—the determination may be regarded with suspicion. ”

“ A thermometer consists of a glass ball having a long thin hollow tube rising out of it and attached to a graduated scale—the bore or hollow of the tube is very small, scarcely sufficient to admit a piece of sewing cotton. The ball or bulb and part of the stalk are filled with mercury by holding a lamp to the ball till the air is nearly all expelled by its expansion—for heat expands air very greatly—and putting the end of the stalk into a vessel of the fluid. ”

“ Others, however, prefer to pay a fixed amount for every thousand gallons used. In such cases, a water-meter is required to record the consumption. We append [Pg 368] a sectional diagram of Kennedy's patent water-meter (Fig. 183) , very widely used. At the bottom is the measuring cylinder, fitted with a piston, (6) , which is made to move perfectly water-tight and free from friction by means of a cylindrical ring of india-rubber, rolling between the body of the piston and the internal surface of the cylinder. ”

“ One set, the convex curves, is for the determination of relative humidity of wet-and-dry-bulb hygrometer or psychrometer; the other, the concave curves, is derived from the vapor pressures and shows the amount of moisture per cubic foot at relative humidities and temperatures when read at the dew-point. The latter curves, therefore, are independent of all variables affecting the wet-bulb readings. They are proportional to vapor pressures, not to density, and, therefore, may be followed from one temperature to another with correctness. ”