September15,1933
INDUSTRIAL A N D ENGINEERING CHEMISTRY
down, and finally the washings are tested to insure complete absence of halides. The tube containing the halide solution, the volume of which should be about 40 cc., is removed from the bottle and an excess of 0.1 N silver nitrate solution added. The precipitate is coagulated in all cases by vigorous stirring by means of a stirring rod, the end of which has been drawn to a dull point.
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349
The procedure followed with the macromethod is essentially that described above; standard macroapparatus is of course used, and the size of the samples so adjusted that the weight of silver halide will be between 225 and 275 mg. Larger samples have been used but are not to be preferred.
PREPARATION OF CRUCIBLE AND TREATMENT OF PRECIPITATE SUMMARY The standard 10-cc. Gooch crucible was used throughout The halogen content of organic compounds may be deterand found to be satisfactory. A smaller crucible if desired mined by means of sodium peroxide-sugar fusion in a micromay be made by cutting off the top of the 10-cc. Gooch. bomb with about the same degree of accuracy and as rapidly Because of the small weight of the precipitate it was found as the macromethod. The weight of the sample required for analyses is much smaller than that required using the macroadvisable to prepare the Gooch in the following way: Full suction is applied and a thick mass of suspended asbestos method. The method is applicable to all compounds which may be sufficient t o form a layer about 3 mm. thick is added. The whole is macerated with a fine stream of distilled water and sucked dry, determined by means of the macromethod, and has the dewashed well with a hot chromic solution and hot concentrated cided advantage that if the above directions are followed a nitric acid and then water, and tapped down with the blunt end destructive explosion is eliminated. of the stirring rod. The asbestos is then washed with 95 per cent Compared to the microgravimetric method the determinaalcohol, dried in an oven at 140” C. for 25 minutes, cooled on a copper block in a desiccator for 10 minutes, and allowed to stand tion of organic halogens is completed much more rapidly in the balance for 15 minutes. and is somewhat more accurate. The precipitate of silver halide is filtered into the prepared Gooch by means of the ointed stirring rod. The test tube is ACKNOWLEDGMEKT washed finally with alcoiol to insure complete removal of the The author is indebted to F. Bremner and A. Kaellgren silver halide and any adhering particles are removed with the feather. The precipitate is washed with 150 cc. of water, to for checking results of analyses. insure complete removal of the nitrates, and then with a little alcohol, dried at 140” C., cooled and weighed as indicated above. LITERATURE CITED The precipitates may be weighed on a good macrobalance but (1) Lemp and Broderson, J . Am. Chem. Soc., 39, 2069 (1917). the samples must of course be weighed on a microbalance. (2) Parr, 8. W., Ibid., 30, 764 (1908). (3) Pregl, F., “Quantitative Organic Microanalysis,” 2nd ed., pp. TREATMENT OF LIQUIDS 123-36, J. & A. Churchill, London, 1930. The most satisfactory method of weighing liquids is by (4) Ibid., p. 70. means of tubes prepared in the same way as the usual micro- RECEIVEDJune 3, 1933. tube (4). This method has also been used in the macroscale and gives good results. The semimicro glass tube should weigh not more than 20 mg. The macro tube should weigh Ground-Glass Junctions not more than 90 mg. The tube found most suitable is illustrated in Figure 2. I n all cases the tube should be HARLANL. BAUMBACH centrifuged to remove the liquid from the capillary and then University of California at Los Angeles, Calif. sealed. The tube is placed a t the bottom of the microcup and covered with the peroxide-sugar mixture and the cap is who have tried to make ground-glass junctions by locked in position. Good results were obtained without shakgrinding a tapered portion of a glass tube into a flanged ing the tube with the peroxide-sugar mixture or b,reaking off end know that it is impossible to procure an evenly ground the capillary before placing the tube in the bomb cup. job, At any one time only a very narrow strip about the circumference is in contact. By using a hollow cone made of TREATMENT OF IODIDES Iodides require a slightly different procedure. Before 0.03-inch (0.75-mm.) thick sheet copper one can grind each acidifying with nitric acid, a few cubic centimeters of nearly piece separately and then place the two together for a slight saturated sulfur dioxide solution are added and, if upon addi- final grinding if necessary. The inside of the cone is used for the grinding of the taper and the tion of the nitric acid the violet color of free iodine appears, outside for t h e g r i n d i n g of the I I more sulfur dioxide solution is quickly added. The acid solusocket. The sheet copperls cut as tion is filtered immediately and silver nitrate solution is added. shown in Figure 1, bent in the form The further treatment is that of the chlorides and the bromides. of a cone, and soldered end to end. Blanks on all reagents must be carefully determined. Standard dimensions c a l l f o r a n This method was found to apply over a large range of orincrease of 0.15 cm. in diameter for ganic compounds and Table I shows a few results obtained on F I G u R E 1 . every 1 cm. measured along the axis some of the organic halogen compounds employed. SHEET COPPER of the cone. The cone can be mounted for the TABLEI. HALOGEN CONTENT OF COMPOUNDS ANALYZED grinding by means of a one-holed rubber stopper HALOGEN SUBSTANCB Calculated Macro Semimicro and a 0.19-inch (5-mm.) wooden dowel placed in % % % the chuck of the lathe or drill press. Turpentine p-Dichlorobenzene 48.16 48.19 48.25 48.15 48.33 or water is applied either to the copper or to the I h m R E 2 43.41 43.55 Dichlorophenol 43.52 43.45 43.54 glass and powdered silicon c a r b i d e is a d d e d . 34.58 34.56 34.59 Bromocamphor This operation is repeated until the grinding is of the desired 34.53 34.56 Dichloraniline 43.73 43.77 43.78 depth. Copper is used in such grinding operations because it 43.80 43.83 Dibromobensene 67.59 67.70 67.76 is extremely tough, yet soft enough to let the fine particles of 67.69 67.84 carborundum imbed in it and grind away the glass. By using p-Iodoacetanilide 48.22 48.16 48.63 48.12 48. OS a hollow cone of copper the same slope is assured for the taper 50.78 Bromobenzene 50.91 50.78 50.86 50.86 as for the socket,
THOSE
d-J
m-Dichlorobenzene
48.25
47.99 48.11
47.95 48.06
RECEIVED July 24, 1933.
