iiiileh
sooner w c r buth types of routs and two silowed mark-
iitg and loss in luster at tlie same time.
Hy grouping tho vnriiishes according t o their elasticity mid tivcraging their dnraljility, tlre following data are obt,nincd: No. of v:f tire time recorded. The average durability measured in this way is in all cases greater over the more elastic color and rulhing varnish coats. BAKEDUXDERC~ATS FOR EXPOSURE T~s~s.--The relative iliiraitiity of the varnislies over the system of air-dried coats and over a baked coat has already been noted. The data of the finishing varnish over the best suited unden:oats were .imilar to those found over the baked coat. Therefore, for .studying tlie diirability of automobile finishing varnishes xit,tiout relation to the undercoats, the one baked coat seems t u be quite as satisfactory as tlie system of built-up air-dried coats. These conclusions are tentative ones, and the study will be continued. A larger number of varnishes, having a kauri reduction of over 100, will be used over a larger number of color coats and over several baking enamels. If it is possible, varnishes varying more widely in othcr plrysical cliaracteri.stics, such as film fartor and watcr resistance, vdl be ineludcd.
..
Acknowledgment
l'ire writer wishes to express his tEinnks to the Edut~atioiial liiireau of the Paint Xanufacturers' Associrttion for doiiating lirnds to eonduct this study and t o I,. . ' 1 I'ulsifcr, of Vttlentine & Company, for his advice and interest in t,lie work. He Jvislies also to express appreciatioii t o A. S . Loudon for valiirtble assistance and t.o several manufaeturcrs for suggestions snd donations uf rarnislies. Fuel Oil Made Dutiable in Antigua~ -Accurding to T r a d e Commissioner H . P. hfacgowan, Antigua has passed an o r d liaiice removing from her free list of imports oil to be used as fuel io oil engines for industrial purposes, and imposts an import duty on such goods a t tlic rate of 15 per cent ad vdorcm uiider t h e griieiai tariff and 10 per cent ad illo ore in under t h e Rritisk preferential tarifl.
diortening the analytical time the progress of the merchandise tlirougli the plant is facilitated, equipment can be used more times around-in general, many savings can be accoin~~lislied.The microscope has its place in certain types of con!rol xork and is becoming more useful daily, particularly in the metals indiistries. J3ut for average analytical control work it cannot conveniently he used-nly chemical methods can 1)eused. Jlicrochemical analytical technic is simply a refinement of the ordinary macro metliods for tile purpose of assaying accurately small amounts of substance. The pioneer in this speri,liized field d cliernicd analysis is Prof. Fritz Pregl, of the University of Graa. The stimulus to his ~ o r on k micro&
R c c e i v e d June
2. 1923.
August, 1925
INDUSTRIAL A-YD E-YGINEERIWG CHEMISTRY
chemical methods was given him in 1910 when, having obtained but minute quantities of a product after a long and complicated investigation, he was faced with the alternative of starting his entire work over again using larger amounts of raw materials or attempting to analyze the exceptionally small amount of material a t hand. He decided to do the latter and, once started on the work of refining the customary methods of organic analysis, he continued his investigations until he had worked out micro methods for practically all types of organic analyses. To him must be given credit for the development of much of the special apparatus which is so necessary to carry on this work. Dificulties in Practical Application of Microchemistry
Microchemical methods have proved their value in purely scientific work. Can they be practically applied? I n considering this question three serious difficulties seemed to present themselves: 1-It w-as assumed that specialized workers were necessary and that the average analyst would not adapt himself to methods in which the factor of error would probably be great due to the smaller quantity of material used. 2-It seemed difficult t o evolve a satisfactory method of sampling. It is troublesome enough a t the present time with macro methods to get a representative sample of a large lot of material. 3-It would be difficult t o find equipment that was not too complicated and not too delicate for practical purposes.
Better to acquaint himself in regard to these questionable points one of the writers visited various laboratories abroad where microchemical technic is the furthest developed and personally interviewed those workers who had accomplished the most in this field. He found that the difficulties mentioned above could easily be overcome. Experience showed that the intelligent analyst could easily adopt these methods, that just as representative a sample could be obtained if the proper precautions were observed as when macro methods were used, and that microchemical apparatus was not more complicated or more subject to breakage than ordinary apparatus. Satisfactory balances having been found, the remaining microchemical apparatus was not so difficult to select and sufficient equipment was purchased to start a series of investigations as to the practicability of these methods in control work. The sampling, as mentioned before, is always difficult. As the amount of material increases the difficulty of obtaining a truly representative sample also grows. This matter of getting a fair sample of the material under examination presents a particularly important problem where micro methods are to be employed. To overcome this difficulty, the sample is collected in the way usual for a macro determination, finely powdered with a special mill originally designed for g r i n d i n g p o p p y s e e d s (extremely easy to clean), and the powder spread out on a paper in a circular form and divided according to the arcompanying diagram. The shaded portions on the diagram represent the area that is selected for repowdering. The operation is repeated several times and in this way a relatively fair sample is obtained. Tests of Micro Methods
To determine the practicability of micro methods a large number of parallel micro and macro assays were run on the same materials. This work has only recently been begun, but data are already available t o show the applirability of these methods.
809
By using 20 to 40 mg. of finely powdered materials in ash determinations, accurate and speedy results are obtained, the entire operation requiring but 20 to 25 minutes. Semi-micro Kjeldahl determination of nitrogen according to the method of Abderhalden and Fodor has worked out very satisfactorily, the time reduction being more than 50 per cent. Only 10 per cent of the material normally required for this assay is used. -4micro method for assaying the alkali and alkali earth salts of organic acids was developed. This method depends upon the conversion of the salts to sulfates. Micro methods for the assay of esters and menthol in oil of peppermint were also tried, with good results using 2-cc. samples of oil. Micro combustions have proved w r y convenient in research work where only small @mountsof synthesized product were available. Conclusion
Although this work represents only a start in the practical utiIization of micro methods, it has nevertheless been sufficient to show that when these methods are properly developed a marked economy in analytical control work will be effected. I n large concerns, where the laboratory costs run between $20,000 and $100,000 a year, with savings of from 50 to 60 per cent which the present results seem to indicate, the matter certainly presents a very promising aspect. C o m p a r a t i v e D a t a o n Macro a n d Micro Analytical Methodsa Micro Macro
%
Ash Determination of Drugs Nux vomica 3.27 7.65 Euphorbia piluifera 8.83 Bryonia root 3.53 Chestnut leaves 4.28 Gentian root 4.04 Bitter orange peel 2.60 Orris root 5.82 Insect flowers 2.88 Juniper berries 5.14 Coriander seed 6.87 French thyme Hvoscvamus 19.30 AGgelica root 14.37 Lobelid herb 6.56 9.64 Valerian root 3.91 Gentian root Ginger root 2 93 Boneset herb 7.31 Sarsaparilla 7.7 Chamomile flowers 11.8 Wormwood 11.96 Yello< mustard 4.31 Larkspur seed 4.93 Juniper berries 2 75 Mallow leaves 16.50 Alkali Salts of Organic Acids Potassium citrate 99.6 Sodium salicylate 99 21 Sodium benzoate 98.8 Sodium acetate 99.85 Sodium benzoate 100.0 Kjeidaiil Determinations of A'ihogen Extract of beef 9.81 8.70 Extract of beef 0 1 1 of Pepperminl A s s a y Ester (Menthyl Acetate) T"
I"
Micro Macro Micro Macro Micro Macro Supplied by
%
3.13 7.65 8.44 3.82 3.81 3.91 2.29 5.65
2.85
4.83 7.0 19.33 13.81 6.55 9.47 3.68 2.95 7.82 7.62 11.4 12.4 4.52 4.97 2.S3 16.39 99.42 99.08 98.4 99. 85 99.26 9.90 8.89 Menthol
5%."
22.54 76.51 76.9 22.00 45.26 9.39 9.15 45.00 10.15 63.33 62.1 10.12 W. Figdor and E. Klarman of this laboratory.
Coarse Cloth from String Bean Fibers-A process for making coarse cloth from the fibers of string beans has been patented in Budapest, Hungary, and is being exploited commercially in Austria. The bean shells are treated like hemp, and the resulting fiber is spun, making a hard but very strong yarn. It is adaptable for making materials for which cotton has been used heretofore. It can also be used in making carpets, curtains, upholstery, and saddlery after it has been properly bleached and printed.
