Silver estimation

Reference may also be made here to the new measurements of specific heat by means of the vacuum calorimeter, to which we have already alluded on page 233. The authors mentioned made use of an apparatus which was essentially the same as that described by Schwers and myself the temperature was measured by means of a platinum wire, through which passed an extremely constant current, so that the resistance could be measured by the potential drop, using a potentiometer. During the heating a silver voltameter was included in the circuit as a control on the measurement of time convenient though this is, I think that as a rule the determination of the duration of the heating current can be made with sufficient accuracy to allow the somewhat troublesome silver estimation to be avoided. 

Addition of silver nitrate to a solution of a chloride in dilute nitric acid gives a white precipitate of silver chloride, AgCl, soluble in ammonia solution. This test may be used for gravimetric or volumetric estimation of chloride the silver chloride can be filtered off, dried and weighed, or the chloride titrated with standard silver nitrate using potassium chromate(VI) or fluorescein as indicator. 

Silver nitrate is used volumetrically to estimate chloride, bromide, cyanide and thiocyanate ions. Potassium chromate or fluorescein is used as an indicator. 

I he methyl iodide is transferred quantitatively (by means of a stream of a carrier gas such as carbon dioxide) to an absorption vessel where it either reacts with alcoholic silver nitrate solution and is finally estimated gravimetrically as Agl, or it is absorbed in an acetic acid solution containing bromine. In the latter case, iodine monobromide is first formed, further oxidation yielding iodic acid, which on subsequent treatment with acid KI solution liberates iodine which is finally estimated with thiosulphate (c/. p. 501). The advantage of this latter method is that six times the original quantity of iodine is finally liberated. 

The two estimates for the first or a parameter of the parabolic fit are the intercepts on the voltage axis of Eig. 3-1, so both procedures arrive at a standard potential of the silver-silver chloride half-cell of 0.2225 V. The accepted modem value is 0.2223 V (Barrow, 1996). 

Photography. Photography (qv) represents one of the oldest industrial uses of iodide. The sensitive silver salt in rapid negative emulsions contains up to 7% or mote silver iodide [7783-96-2], Agl. Erom 1969 to 1985 estimates on iodine consumption for this purpose varied from 150 to 270 t/yr (66). Ttiphenylphosphonium iodide is also among the iodine derivatives used in photography. This derivative permits faster development and higher contrast photography. 

The American cordillera extending from Alaska to BoUvia has been the most productive source of silver wherever it is associated with Tertiary age intmsive volcanic rocks, mosdy concentrated by hydrothermal action. The largest producing mine in the cordillera is at Potosi, BoUvia, where the total silver output since the 1500s is estimated at over 31,000 metric tons. 

Resources. World resources of silver are estimated to be about half a million tons. However, only about 250,000 metric tons are considered economically recoverable reserves. These are associated with ores of copper, gold, lead, and 2inc, and extraction depends on the economic recovery of those metals. Canada and the CIS vie for the greatest reserves of silver in the ground. 

Mine Production of Silver. World production of silver by region is given in Table 3. Some 900,000 metric tons are estimated to have been mined since early times. By the year 1500 world mine production was about 50 t/yr. In 1992 world production exceeded 14,900 metric tons. EoUowing the breakup of tfie Soviet Union, previously undisclosed data showed that the USSR led wodd silver production during 1979—1980 at about 1550 metric tons. During the early 1990s the production in this region exceeded 2000 t/yr. 

The cost of various silver compounds is a function of the silver market price. In 1980, the estimated usage of silver ia the United States was 3730 metric tons (120 X 10 troy oz) (23). This silver is derived from silver mined within the United States silver recycled or reclaimed from secondary sources, eg, coiaage, flatware, jewelry, and photographic materials and imported silver. In 1980, Canada, Mexico, and Pern, the principal exporters of silver to the United States, shipped 1670 tons (53.8 x 10 troy oz) as silver buUion and silver compounds. U.S. imported 2799 t and exported 964 t ia 1988 (23). 

As of the 1990s, the EPA recommends that the dissolved form of silver be used as a better estimate of the bioavailable fraction and recommends using 85% of the total recoverable quantity. Thus, in fresh water at hardnesses of 50, 100, and 200 mg/L CaCO, the concentration of dissolved silver should not exceed 1.0, 3.5, and 11 Fg/L, respectively. The concentration of dissolved silver in salt water should not exceed 1.9 Fg/L (46). 

Open-pit zinc mining is not common, since most mines ate below the surface. The Kidd Creek Mine in Ontario, Canada, is a combination open-pit—underground mine. It is one of the richest deposits in the world with an estimated 62.5 x 10 t grading 7.08% zinc, 1.33% copper, and 151 g silver (14). Underground mining methods include room-and-pdlar, shrinkage, cut-and-fill, and square set. In the United States, ca 20 mines account for more than 98% of zinc production. 

EtOH). No methoxyl is present. It forms a series of crystalline double chlorides with cadmium, zinc or copper, does not give the thalleioquin reaction, and solutions of its sulphate are not fluorescent. It is diacidie and forms two series of salts of which the nitrate, B. HNOj, crystallises in minute prisms, m.p. 196°, insoluble in water. Cinchonamine hydrochloride, B. HCl, laminae or B. HCl. HjO, cubical crystals, has been suggested for use in the estimation of nitrates. When warmed with strong nitric acid the alkaloid furnishes dinitrocinchonamine. It gives an amorphous, monoacetyl derivative, and forms a methiodide, m.p. 208 , which with silver oxide yields an amorphous methylcinchonamine. Raymond-Hamet found that cinchonamine ves typical indole colour reactions and is probably an indole alkaloid. This seems to have been... 

As it can be seen in Fig. 1(c), there is a minimum size for the silver nitrate filling. If we assume that the polarisability of the enclosed material is identical to the bulk value, we can estimate the CNT cavity polarisability by using the measured minimal filled CNT. Then, if the cavity polarisability is size dependent, this approach can be used to measure the tube cavity properties, and we could also predict the wetting properties (or minimal filled tubes) for different materials. 

Hydrocyanic acid may be approximately estimated by dissolving 1 gram of oil in 5 c.c. of alcohol, and adding 50 c.c. of water. Then add ammonio-silver nitrate solution and shake well. Acidify slightly with nitric acid, and collect, wash, and dry the silver cyanide precipitated. Ignite and weigh the silver, 4 parts of which correspond to practically 1 of hydrocyanic acid. 

Sodium Chloride [25]. Sodium chloride estimation is based on sodium titration. To 20 ml of a 1 1 mixture of toluene (xylene) isopropyl alcohol, add a 1-ml sample of oil-base mud, stirring constantly and 75 to 100 ml of distilled water. Add 8-10 drops of phenolphthalein indicator solution and titrate the mixture with H SO (N/10) until the red (pink) color, if any, disappears. Add 1 ml of potassium chromate to the mixture and titrate with 0.282N AgNO (silver nitrate, 1 ml = 0.001 g chloride ions) until the water portion color changes from yellow to orange. Then... 

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