An Introductory Course of Quantitative Chemical Analysis Part 27

___________________________________________________________________________ | | | | BURETTE | DIFFERENCE | OBSERVED | DIFFERENCE | CALCULATED READINGS | | WEIGHTS | | CORRECTION _______________|______________|______________|______________|______________ 0.02 | | 16.27 | | 10.12 | 10.10 | 26.35 | 10.08 | -.02 20.09 | 9.97 | 36.26 | 9.91 | -.06 30.16 | 10.07 | 46.34 | 10.08 | +.01 40.19 | 10.03 | 56.31 | 9.97 | -.06 50.00 | 9.81 | 66.17 | 9.86 | +.05 _______________|______________|______________|______________|______________

These data to be obtained in duplicate for each burette.

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DETERMINATION OF COMPARATIVE STRENGTH HCl vs. NaOH

___________________________________________________________________________ | | DETERMINATION | I | II _________________________|________________________|________________________ | | | Corrected | Corrected Final Reading HCl | 48.17 48.08 | 43.20 43.14 Initial Reading HCl | 0.12 .12 | .17 .17 | ----- ----- | ----- ----- | 47.96 | 42.97 | | | Corrected | Corrected Final Reading HCl | 46.36 46.29 | 40.51 40.37 Initial Reading HCl | 1.75 1.75 | .50 .50 | ----- ----- | ----- ----- | 44.54 | 39.87 | | log cc. NaOH | 1.6468 | 1.6008 colog cc. HCl | 8.3192 | 8.3668 | ------ | ------ | 9.9680 - 10 | 9.9676 - 10 1 cc. HCl | .9290 cc. NaOH | .9282 cc. NaOH Mean | .9286 | _________________________|________________________|________________________

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STANDARDIZATION OF HYDROCHLORIC ACID ===================================================================== | | Weight sample and tube| 9.1793 | 8.1731 | 8.1731 | 6.9187 | ------ | ------ Weight sample | 1.0062 | 1.2544 | | Final Reading HCl | 39.97 39.83 | 49.90 49.77 Initial Reading HCl | .00 .00 | .04 .04 | ----- ----- | ----- ----- | 39.83 | 49.73 | | Final Reading NaOH | .26 .26 | .67 .67 Initial Reading NaOH | .12 .12 | .36 .36 | --- --- | --- --- | .14 | .31 | | | .14 | .31 Corrected cc. HCl | 39.83 - ----- = 39.68 | 49.73 - ----- = 49.40 | .9286 | .9286 | | log sample | 0.0025 | 0.0983 colog cc | 8.4014 - 10 | 8.3063 - 10 colog milli equivalent| 1.2757 | 1.2757 | ------ | ------ | 9.6796 - 10 | 9.6803 - 10 | | Normal value HCl | .4782 | .4789 Mean | .4786 | | | =====================================================================

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DETERMINATION OF CHLORINE IN CHLORIDE, SAMPLE No.

===================================================================== | | Weight sample and tube| 16.1721 | 15.9976 | 15.9976 | 15.7117 | ------- | ------- Weight sample | .1745 | .2859 | | Weight crucible | | + precipitate | 14.4496 | 15.6915 Constant weights | 14.4487 | 15.6915 | 14.4485 | | | Weight crucible | 14.2216 | 15.3196 Constant weight | 14.2216 | 15.3194 | | Weight AgCl | .2269 | .3721 | | log Cl | 1.5496 | 1.5496 log weight AgCl | 9.3558 - 10 | 9.5706 - 10 log 100 | 2.0000 | 2.0000 colog AgCl | 7.8438 - 10 | 7.7438 - 10 colog sample | 0.7583 | 0.5438 | ------- | ------- | 1.5075 | 1.5078 | | Cl in sample No. | 32.18% | 32.20% | | =====================================================================

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STRENGTH OF REAGENTS

The concentrations given in this table are those suggested for use in the procedures described in the foregoing pages. It is obvious, however, that an exact adherence to these quant.i.ties is not essential.

Approx. Approx.

Grams relation relation per to normal to molal liter. solution solution

Ammonium oxalate, (NH_{4})_{2}C_{2}O_{4}.H_{2}O 40 0.5N 0.25 Barium chloride, BaCl_{2}.2H_{2}O 25 0.2N 0.1 Magnesium ammonium chloride (of MgCl_{2}) 71 1.5N 0.75 Mercuric chloride, HgCl_{2} 45 0.33N 0.66 Pota.s.sium hydroxide, KOH (sp. gr. 1.27) 480 Pota.s.sium thiocyanate, KSCN 5 0.05N 0.55 Silver nitrate, AgNO_{3} 21 0.125N 0.125 Sodium hydroxide, NaOH 100 2.5N 2.5 Sodium carbonate. Na_{2}CO_{3} 159 3N 1.5 Sodium phosphate, Na_{2}HPO_{4}.12H_{2}O 90 0.5N or 0.75N 0.25

Stannous chloride, SnCl_{2}, made by saturating hydrochloric acid (sp.

gr. 1.2) with tin, diluting with an equal volume of water, and adding a slight excess of acid from time to time. A strip of metallic tin is kept in the bottle.

A solution of ammonium molybdate is best prepared as follows: Stir 100 grams of molybdic acid (MoO_{3}) into 400 cc. of cold, distilled water. Add 80 cc. of concentrated ammonium hydroxide (sp. gr. 0.90).

Filter, and pour the filtrate slowly, with constant stirring, into a mixture of 400 cc. concentrated nitric acid (sp. gr. 1.42) and 600 cc. of water. Add to the mixture about 0.05 gram of microcosmic salt.

Filter, after allowing the whole to stand for 24 hours.

The following data regarding the common acids and aqueous ammonia are based upon percentages given in the Standard Tables of the Manufacturing Chemists' a.s.sociation of the United States [!J.S.C.I.!, 24 (1905), 787-790]. All gravities are taken at 15.5C. and compared with water at the same temperature.

Aqueous ammonia (sp. gr. 0.96) contains 9.91 per cent NH_{3} by weight, and corresponds to a 5.6 N and 5.6 molal solution.

Aqueous ammonia (sp. gr. 0.90) contains 28.52 per cent NH_{3} by weight, and corresponds to a 5.6 N and 5.6 molal solution.

Hydrochloric acid (sp. gr. 1.12) contains 23.81 per cent HCl by weight, and corresponds to a 7.3 N and 7.3 molal solution.

Hydrochloric acid (sp. gr. 1.20) contains 39.80 per cent HCl by weight, and corresponds to a 13.1 N and 13.1 molal solution.

Nitric acid (sp. gr. 1.20) contains 32.25 per cent HNO_{3} by weight, and corresponds to a 6.1 N and 6.1 molal solution:

Nitric acid (sp. gr. 1.42) contains 69.96 per cent HNO_{3} by weight, and corresponds to a 15.8 N and 15.8 molal solution.

Sulphuric acid (sp. gr. 1.8354) contains 93.19 per cent H_{2}SO_{4} by weight, and corresponds to a 34.8 N or 17.4 molal solution.

Sulphuric acid (sp. gr. 1.18) contains 24.74 per cent H_{2}SO_{4} by weight, and corresponds to a 5.9 N or 2.95 molal solution.

The term !normal! (N), as used above, has the same significance as in volumetric a.n.a.lyses. The molal solution is a.s.sumed to contain one molecular weight in grams in a liter of solution.

DENSITIES AND VOLUMES OF WATER AT TEMPERATURES FROM 15-30C.

Temperature Density. Volume.

Centigrade.

4 1.000000 1.000000 15 0.999126 1.000874 16 0.998970 1.001031 17 0.998801 1.001200 18 0.998622 1.001380 19 0.998432 1.001571 20 0.998230 1.001773 21 0.998019 1.001985 22 0.997797 1.002208 23 0.997565 1.002441 24 0.997323 1.002685 25 0.997071 1.002938 26 0.996810 1.003201 27 0.996539 1.003473 28 0.996259 1.003755 29 0.995971 1.004046 30 0.995673 1.004346

Authority: Landolt, Bornstein, and Meyerhoffer's !Tabellen!, third edition.

CORRECTIONS FOR CHANGE OF TEMPERATURE OF STANDARD SOLUTIONS

The values below are average values computed from data relating to a considerable number of solutions. They are sufficiently accurate for use in chemical a.n.a.lyses, except in the comparatively few cases where the highest attainable accuracy is demanded in chemical investigations. The expansion coefficients should then be carefully determined for the solutions employed. For a compilation of the existing data, consult Landolt, Bornstein, and Meyerhoffer's !Tabellen!, third edition.

Corrections for 1 cc.

Concentration. of solution between 15 and 35C.

Normal .00029 0.5 Normal .00025 0.1 Normal or more dilute solutions .00020

The volume of solution used should be multiplied by the values given, and that product multiplied by the number of degrees which the temperature of the solution varies from the standard temperature selected for the laboratory. The total correction thus found is subtracted from the observed burette reading if the temperature is higher than the standard, or added, if it is lower. Corrections are not usually necessary for variations of temperature of 2C. or less.

INTERNATIONAL ATOMIC WEIGHTS

========================================================== | | | | 1920 | | 1920 _________________|_________|___________________|__________ | | | Aluminium Al | 27.1 | Molybdenum Mo | 96.0 Antimony Sb | 120.2 | Neodymium Nd | 144.3 Argon A | 39.9 | Neon Ne | 20.2 a.r.s.enic As | 74.96 | Nickel Ni | 58.68 Barium Ba | 137.37 | Nitrogen N | 14.008 Bis.m.u.th Bi | 208.0 | Osmium Os | 190.9 Boron B | 11.0 | Oxygen O | 16.00 Bromine Br | 79.92 | Palladium Pd | 106.7 Cadmium Cd | 112.40 | Phosphorus P | 31.04 Caesium Cs | 132.81 | Platinum Pt | 195.2 Calcium Ca | 40.07 | Pota.s.sium K | 39.10 Carbon C | 12.005 | Praseodymium Pr | 140.9 Cerium Ce | 140.25 | Radium Ra | 226.0 Chlorine Cl | 35.46 | Rhodium Rh | 102.9 Chromium Cr | 52.0 | Rubidium Rb | 85.45 Cobalt Co | 58.97 | Ruthenium Ru | 101.7 Columbium Cb | 93.1 | Samarium Sm | 150.4 Copper Cu | 63.57 | Scandium Sc | 44.1 Dysprosium Dy | 162.5 | Selenium Se | 79.2 Erbium Er | 167.7 | Silicon Si | 28.3 Europium Eu | 152.0 | Silver Ag | 107.88 Fluorine Fl | 19.0 | Sodium Na | 23.00 Gadolinium Gd | 157.3 | Strontium Sr | 87.63 Gallium Ga | 69.9 | Sulphur S | 32.06 Germanium Ge | 72.5 | Tantalum Ta | 181.5 Glucinum Gl | 9.1 | Tellurium Te | 127.5 Gold Au | 197.2 | Terbium Tb | 159.2 Helium He | 4.00 | Thallium Tl | 204.0 Hydrogen H | 1.008 | Thorium Th | 232.4 Indium In | 114.8 | Thulium Tm | 168.5 Iodine I | 126.92 | Tin Sn | 118.7 Iridium Ir | 193.1 | t.i.tanium Ti | 48.1 Iron Fe | 55.84 | Tungsten W | 184.0 Krypton Kr | 82.92 | Uranium U | 238.2 Lanthanum La | 139.0 | Vanadium V | 51.0 Lead Pb | 207.2 | Xenon Xe | 130.2 Lithium Li | 6.94 | Ytterbium Yb | 173.5 Lutecium Lu | 175.0 | Yttrium Y | 88.7 Magnesium Mg | 24.32 | Zinc Zn | 65.37 Manganese Mn | 54.93 | Zirconium Zr | 90.6 Mercury Hg | 200.6 | | ==========================================================