I N D U S T R I A L AND ENGINEERING CHEMISTRY
370
a current of hydrogen chloride gas through the heated acid after the addition of a small amount of a reducing agent. Five hundred cubic centimeters of sulfuric acid were treated in a distilling flask with 2 grams of sodium bisulfite. A current of hydrochloric acid vapor obtained by boiling this acid was led through the distilling flask, a sufficiently strong flame being kept under the flask to prevent condensation of hydro-
Vol. 16, No. 4
chloric acid. The completion of the purification may be checked by a test of the hydrochloric acid distillate. A typical series is given in Table 11. These methods have been found very convenient and reliable for laboratory use, and it is believed that they will be,of service to chemists, especially in investigations that may have a legal significance.
Fritted Glass Filter Disks1 By Paul H.Prausnitz SCHOTT & GBN.,JENA,GERMANY
0 overcome the obvious disadvantages of filter paper in many laboratory procedures, glass filter disks of Jena glass are now offered. These disks are made somewhat after the design of Filtros, the disks being formed by sintering or fritting glass powdered to specific sized particles. The larger the particles the coarser the filter. So far, those capable of retaining barium sulfate freshly precipitated in a hot liquid represent the upper limit in the series. By using a series of thcse disks, fractional filtration according to particle size may be made. These disks are fused into the funnel, thistle tube, Soxhlet apparatus, or wherever required. They thus forin a substitute for the Buchner funnel as well as for the extraction thimble. In the case of the Soxhlet apparatus, the disks can be sealed at about one-fourth or one-third of the lehgth of the extraction tube above the base-the third tube added to the extractor connecting the compartments on both sides of the filter disk to enable the air in the lower compartment to be displaced by the liquid passing through
T
FIG. I-FUNNELS USINGGLASSFILTERDISKS
the filter. If this is not convenient, the filter disk can be sealed in a tube and thus become a substitute for the paper cartridge and be used in like manner in the extraction tube. In qualitative analysis a filter of this design can be used with a series of test tubes having a side arm for suction, 1 Received
December 26, 1923.
and many separations, as of silver, mercury, antimony; copper, aluminium, iron, barium, and magnesium, can be made rapidly and satisfactorily. Precipitates can be rapidly filtered, washed, dissolved, etc., the test tubes being re placed as required. In quantitative analysis it is believed these disks may easily replace the Gooch crucible. While the temperatures at which precipitates should be dried or ignited should not exceed 600" C. and care must be exercised in cooling the new filter, it is also possible to prepare these filters of quartz and heat them to higher temperatures in electric furnaces or by other means. Where filter papers are used, however, the higher temperatures are frequently necessary only to remove the trace of carbon and reduce the paper to a white ash. Where this is not required, drying at from 110" to 140" C. is sufficient. Constant weight can be obtained more easily and quickly with the glass filter disks or crucibles than where paper, asbestos, infusorial earth, or other media are employed. For filtering large quantities of liquids disks may be used in funnels of 60, 90, or 120 mm. diameter, which are now available. Larger ones are in course of construction. The plates may also be used for pharmaceutical purposes in cy1in- FIG,2-C~oss SECTION OF SINGLE ders of anv reasonable FILTER DISK height, and ;here pressure is preferred to suction apparatus wholly of glass can be prepared. Small quantities of precipitates are often found in large volumes of fluids; in such cases the glass filter funnel can be immersed in the fluid, which is removed rapidly by the aid of suction. These filters have also been used for filtering air or gas, to purify mercury, and have even been considered for diaphragms in electrochemical experiments. They are said to be easily cleaned by reverse washing and by means of chemical solvents, and for some operations the possibility of seeing what is taking place is a great advantage. Isolation of Titanium Isolation of titanium on a commercial scale has been made possible as a result of research work conducted for the past several years by Simon J. Lubowsky, research engineer of the Metal & Thermit Corporation. This metal, which heretofore has been obtainable only as a laboratory curiosity, is now to be had in commercial quantities. The principle of this new method of isolation is applicable on a commercial scale to many of t h e rare elements, although Mr. Lubowsky has carried his work to completion only in respect to metallic titanium.
