June, 1912
T H E JOUR.VAL OF Ii2'DCSTRIilL .412'D E.YGIiYEERII1-G C ; H E J / I S T R 5 ~ .
mine their value The determination of the naturc and amount of impurities in organic and inorganic chemicals, oils, resins, gums, balsams, etc., taxes the resources of any chemist, and the pharmaceutical chemist is often driven t o the expedient of rejecting clearly unsatisfactory materials on account of the presence of unidentified impurities. In choosing materials it is understood t h a t certain amounts of harmless impurities must be permitted in all medicinal substances otherwise their cost would be prohibitive. Having determined t h a t the crude materials are satisfactory, the manufacturing processes must be controlled b y the examination of preparations in different stages of manufacture in order t o give directions for finishing products of proper strength and composition. The finished products must then be examined t o determine their compliance with standards of strength and purity, and also b y aging experiments t o determine something of their keeping qualities. It is said t h a t it is impossible t o remain stationary; if this is true no manufacturer can stop when he has accomplished what has been outlined above; he must strive t o advance. Many of the analytical methods used in this work leave much t o be desired and a constant effort must be made t o improve them. Manufacturing processes must be improved in order t o produce better products and, t o make them more economically, new processes and new products must also be devised. With the enactment of food and drug laws the inspection of drug products became a very important division of pharmaceutical work. Extremely valuable results have already been achieved by workers in this field and b y conservative work much more will be accomplished. The sensational methods and arbitrary rulings which have, in a few instances, been resorted to, are, however, t o be greatly deplored. Having discussed our subject in a general way i t may be of interest t o give some definite idea of the number of substances with which the pharmaceutical chemist has t o deal. A certain manufacturing house lists about four thousand products, in the preparation of which about seven hundred different materials, which must be examined chemically, are used. Pharmaceutical chemistry presents an inviting field of work t o the young chemist. Comparatively little is known concerningthecomposition of many of the hundreds of vegetable drugs in use. Even in case of some of the most important drugs our knowledge is
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very defective Ergot may be cited as an example, the most important contributions to our knowledge of its composition having been made within the last few years, although its study has been undertaken b y many eminent chemists during a period extending over many years. The composition of the vegetable drugs alone offers an interesting and impnrtant field of work for the pharmaceutical chemist for generations t o come. The effect of cultivation upon t h e chemical composition of medicinal plants has been almost entirely neglected, although the remarkable increase in the quinine content of cinchona bark through cultivation has long been known. The relation of chemical constitution t o physiological action, and the study of the enzymes and hormones which may be used medicinally are merely suggestive of the broad fields which await the pharmaceutical chemist of the future. While a review of the progress of pharmacy would not be appropriate here it may not be out of place t o call attention to the several lines of cooperative analytical work which are being carried on. The keeping quality of medicinal preparations has already been referred to and this subject has had the serious consideration of manufacturers for a number of years. Several of the largest manufacturers have collaborated on this work and have published the results already obtained in the form of a brochure on the "Stability of the Drug Extracts " The work has shown t h a t preparations of this class are as a rule remarkably stable. The pharmaceutical division of this society has a Committee on Quantitative Methods whose function is the study and improvement of analytical methods used in pharmaceutical work. The U. S. Pharmacopoeia and the National Formulary, which are our official standards for medicinal substances, are now being revised, and in these great undertakings a large number of workers in all branches of pharmacy are collaborating. As these works do not include all articles which are commonly used in medicine, the American Pharmaceutical Association has a standing committee for the establishment of unofficial standards in which all classes of pharmaceutical workers are represented. As the pharmaceutical chemists are thus striving to advance this branch of chemistry, it is t o be hoped t h a t they will not neglect any opportunity for furthering closer relations with one another and with chemists in other lines of work. F. R. E L D R E D .
ORIGINAL PAPERS STRUCTURE OF GALVANIZED IRON. BY
W A L T E R ARTHUR AND W I L L I A M
H
XI'ALKER
Received December 11, 191 1
Galvanized iron, by which term in this article we shall include all zinc protected iron, consists not of a sheet of iron covered with a layer or skin of pure zinc,
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as one might expect, but, on the contrary, of a complicated system of iron-zinc compounds, starting with pure zinc on the outside and passing through these alloys t o the iron base within. We shall consider the structure of zinc protected iron under the three heads: I . Hot galvanized-material made by passing the iron through a bath of melted zinc
2 . Shcrardized-.-thc articlr heated in thc presence o f finely ilividrd zinc and zinc oxide. 3. Wet or 1Slectrogalvanizcd--a layer of either zinc or a zinc alloy deposited rlcctrolytically on the iron article from a n aqiiaous b a t h . By examining t h r zinc-iron alloy diagrani construet.ed hy v. Vcgi3sack: which i s rrproducrd i n part as Fiw. I , wc see that hy r:iisi$>g l h c ttmpcwtiirr iron
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point i t on the iliag'ram rrpr n t s the rnzixiniiim solubility of zinc FcZn,. arid it i s prohahi>-this siitiiratcd solid solution which is noticeablc i n certain scctions of galvanizc~iiron. h fraction of onc per cont. (0.i - - o . 7 p c ~ cent.) f iron rrmains clissolveil in t,hc zinc :Liter solidificatioii. -Crmsiclrr first t h r
