192
INDUSTRJAL AND ELVGINEERINQCHEMISTRY
dertake the manufacture of many new articles. In the optical field none were better equipped for such an undertaking than Bausch & Lomb, and they immediately expanded to meet the demand. Of the instruments which they began to make then, perhaps the ones of mast importance to the chemist are those which utilize optical properties and principles for the measurement of physical characteristics of materials. These instruments were developed especiaUy to meet the needs of chemical and allied industries for quicker methods of analysis and for the study of special properties of materials. Only a few can be mentioned here, but perhaps these example3 will indicate the extent to which the chemist is using optical methuds nowadays. The colorimeter in its various forms enables the chemist to determine quantitatively io a few minutes a substance which might take hours to determine gravimetrically or volumetrically. It Can be used, of course, only for reactions where colors can be established which will he permauent at least for the duration of the experiment, but many such sf reactions are those which are difficultto treat Microscope Buttt by other methods. The hi&gi& chemist, by 3. J. Dausch for example, uses the colorimeter to a great extent, since his routine gravimetric analysis is particularly difficult. In the inorganic field, mauy metals which appear as im. methods are purities in such minute quantities that extremely difficult cannot only be detected but accurately determincd. The colorimeter has also been modified to meet the demand for quick methods of determining hydrogen-ion concentration. Refractive index as a characteristic propc,.tyhas also in for its share of attention in special determinations, especially gives in the aSe of liquids, ~h~ ~ b b 6typeof refractometer the refractive index from 1.3000 to 1.7000 with an accuracy of 0,0001 to 0.0002, this accuracy depending on thc substance and the of the being used, lt may be used on liquidsandtransparen~l;dson surface "y which a be ~ h ~ i
fractometer will determioe the index of a liquid over a range of 1.3000 to 1.5400 with an accuracy of better than one in the fourth decimal place if the temperature of the liquid is controlled. The saccharimeter has been long used for determining the concentration of sugar solutions. It is simply an instrument for measuring the rotation of the plane of polarization of light, but requires very careful design if it is to be accurate andrapid. Whenthecompany decided to a saccharimet-, it consulted the leading Micro- sugar chemists in the country 8EOpe and then designed an instrument incorporating their best ideas. Its controlled accuracy is 0.05 S., which is equivalent to about 13 mg. oi sugar per 100 cc. of solution. Spectral analysis has become industrially important in recent Years. It is of two types. one of which is the true analysis of bright line and band spectra and the other of which is spectrophotometric analysis. The latter is related particularly to the
Vol. 21, No. 2
colors transmitted through various substances or reflected from them. Both of these types of spectral analysis are becoming more and more quantitative. The spectrograph, revealing the lines characteristic of the various elements even when only traces are present, offers a method of detection and evaluation which goes well beyond the limits of ordinary chemical analysis. To meet demands along these lines, a complete line of spectroscopes has been developed, from the simple qualitative hand spectroscope covering the visible range to the large quartz spectrograph covering the range from 7000 A. in the visible to 2100 A. in the ultraviolet. These are designed for both visual and photographic methods and several of the models serve as monochromators in both the visible and the ultra-violet. For spectrophotometric analysis the company has developed a universal spectrophotometer of the polarizing type. With this instrument almost any material can be examined, whether it be a transparent solid, an opaque solid, or a liquid. By means Of a determination of transmission values and extinction coefficients, the concentrations of dye and stain sohitions can be abtaincd where chemical methods are exceedingly laborious or fail comP1eteiY. The colloid chemist has been furnished with a very powerful aid in the form of a simplified slit ultra-microscope. In this instrument a very strong illumination enters the specimen, from the side, at right angles with the axis of the microscope. Colloidal particles in suspension, which are too small to be visible under the highest power in the ordinary microscope, appear as bright points in a dark field by means of diffracted light. These few paragraphs will convey to ihe reader some idea of the manifold activities of the Bausch & Lamb organization, although thcy touch upon only a small part of the company's interests. The last few decades have witnessed an astounding rate of Progress in all the natural sciences. Each discovery in a given science has provided means of attack on the problems of the 0th- sciences. As fast as progress has been realized in optical Science, chemistry has employed the results of that progress in the solution of its own problems. To the end that chemistry and all the other sciences may continue to progress evep at an axelcrated rate, the Bausch & Lomb Optical Company is applying its resources to the continued developmcnt of optical apparatus ~ ~ designed ~ ~to meet i their ~ ever ~ growing ~ ~needs. -
J. W. Fonn~sr
Stirrer from Windshield Wiper' A. V. Motsinger RBNVIL, N. J.
HE w r i t e r , recently i n need of a stirrer for use in a melting-point determination, found that the mechanical suction part of an automobile windshield wiper with the rod attached to it made an ideal stirrer as the speed and stroke could be easily adjusted, A a m wa6 made from pieee o f ere the wire and ePer attached to it as shown the ~
aceon,panying This stirrer is inexpensive and can be used in a n y laboratory
where there is a suction line, 1
Reccived September 27, 1928.
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