May, 10%
I S D C S T R I A L , 4 5 0 ESGISEERI.VG CHEMISTRY
ment could have been continued indefinitely. A sixth generation of albino rats was similarly reared before the expariment was discontinued. Conclusions
I t is apparent that wheat germ extract so prepared possesses valuable nutritive properties and should find a considerable use in human nutrition. il waste product of the flour mills, which has previously been used only as a cattle feed within a rather narrow area near the flour mills, may by this method be converted into a valuable, concentrated food for human beings and particularly for infants and invalids. I t may be used in many ways as a supplement to the ordinary diet incorporated in food products of various kinds or it may
503
even be used as a partial substitute for table sugar. I n limited numbers of experiments made with human subjects the results so far obtained lead to the conclusion that this extract may be extremely valuable as a modifier of milk for infants. The readiness with which it is assimilated and its ease of toleration add further to its possible usefulness in any disease caused by deficiencies which it may make up. Acknowledgment
The author wishes to express his appreciation for the valuable assistance given by H. D. Grigsby and N. M. Cregor in developing the process by which this extract is made on a commercial scale. Due credit is also given to Laura Ashe and D . P. Fischer for their contributions to this paper.
Action of Calcium Chloride Brines on Galvanized Coatings' By Arthur C. White THE Dou- CHEMICAL Co.,MIDLAND, hlIcH.
M
ETALLIC zinc in the form of galvanized coating is used in piping, shell coolers, agitators, and the usual steeI generally protected by an extremely thin film of a plate tank filled with brine of any sort, makes an ideal mixture of basic carbonate, carbonate, oxide, and situation for both chemical and electrolytic corrosion. The old practice of allowing the zinc coating to disappear hydroxide. This coating, if the surface is kept dry, is a as rapidly as it cared to-which was often very rapid indeed decided protection against further oxidation and corrosion. In water, or in brines containing carbon dioxide in solution, -without making any attempt to conserve it, was an ecopart of this protective coating passes into solution as the nomic waste. The fact that galvanizing acts only as a prosparingly soluble bicarbonate, while the bulk of it, in suspen- tective coating and not as a corrosion-resisting metal, and will eventually Ydisappear, offers sion, gives the milky apno excuse for the neglect to pearance so often noticed preserve it as long as possiin brine systems. Metallic zinc when used as a coating for iron forms ble. Every month or year As the original coating of a protective coating upon itself. Galvanized coatings of retention of this coating zinc is slowly oxidized, carmay form a large part of the metal exposed to the action adds that quota to the life bonated, and removed, it of the calcium brine in a refrigeration installation. of the comparatively expenfinally exposes the iron at The degree of soluble alkalinity present in the brine sive cans and cuts deprecisome point where the galhas a decided effect on the corrosion of the galvanizing. ation costs. vanizing was thin and alThe effect of alkalinity on galvanized coatings is the lows corrosion of the iron reverse of that upon iron. by air oxidation to take Corrosion by Different Commercial calcium chlorides now on the market Brands of Commercial place. The electrolytic acshow decided corrosive action due to their high soluCalcium Chloride tion then set up accelerates ble alkalinity. Weak brines show more corrosive action the decomposition of the than do those of higher gravity for the same degree of zinc metal. iifter the galThat nearly all brands of alkalinity. With brines of low alkalinity the presence v a n i z i n g has completely commercial calcium chloof ammonia or ammonium chlorides tend to increase disappeared, local electroride do attack zinc and galthe amount of corrosion. lytic a c t i o n s start work vanized coatings rapidly is upon the iron itself. shown by the following Considerable a t t e n t i o n experiment : has been given, papers have been read, and numerous articles Plate I s h o w the effect of the action on galvanized written on the subject of corrosion of iron and steel in re- iron of five samples of comniercial calcium chloride from frigerating plants,2,3*4 but very little mention seems to have four different manufacturers and each with a different been made of the action of calcium chloride brines on gal- alkalinity when made up into brines of 1.20 gravity a t vanized coatings as differentiated from iron itself. The tend- 20° c. ency in the past has been to lay stress only on the corrosion The strip in Tube 1, after approximately 70 days' imof the iron and to neglect all other metals that may be mersion in neutral brine, shows no corrosion whatever (alpresent in commercial plants. though owing to the effect of lighting when the photograph A large part of the metal surface exposed to the action of was taken it appears as though slight corrosion had taken the refrigerating brine in the modern ice plant consists of place). the outside walls of the galvanized ice cans. This, in conThe test strip in Tube 2 immersed in a brine having an junction with the smaller proportion of black iron surfaces alkalinity of 1.5 cc. 0.1 N per 100 cc. (0.004 per cent Ca(OH)2 or 0.15 per cent normality) had small isolated areas where 1 Received November 19, 1924. corrosion had taken place, these showing the customary 9 Poste and Donauer, M i l k Dealer, February 1923 white deposit and evidently occurring where the zinc coatHull I c e and Refrigeralion, March, 1923 ' Speller J A m SOC.Refrrg Eng , 8, 216 (1921) ing was thin.
not removed by cleaning the test strips. 2 solution with an alknliirity corresponding to 5 cc. 0.1 .Iijer 100 cc. (0.035ncr rent CdOII),, or 11.5 m r cent nonnalitvt h w d t h a t tlie gilvanizing iii irregular pat'ches was somewl& darkened and slightly corroded, altlioirgli approximately 75 per cent of the immersed strip showed the original bright surface.
3--'M'ith alkalinities of 15.9 CC. 0.1 N per 100 cc. (0.048per rent CdOW)., or 1.59 ET cent iiormalitv) and of 1H.i ce. 0. 1 N per 100 Cc. (0.0~1per &it C ~ ( O H ) or * I:& per ceiit iiormality). the zinc of the test pieces was practically eliminated, with the exception of the zinc-iron alloys and small patches of zinc oxide. A heavy grayish white precipitate was depositcd in the bottom of the test tubes. 4-With an alkalinity oi 58 ec. 0.1 N per 1OO cc., correspondTub?. .
.
I Mfrr . n nav\.. 70
2 .,I :1u
li
a
1 C
D
3
50
50
i
Plrtr I
"
,
,-.
~
.
a very much worse corrosive action resulted than with any of the other three solutions for an equal time period. Not olily was all the galvanizing and the underlying sinc-iron alloy entirely removed, but the strip was practically coated with a
d u e to eorri,sioti was tliiak atid slisiiy and adhered to the slimy deposit of zinc carboilate and hydrated zinc oxide, whilr test strip. Strips 4 aud 5, witlr alkalinities, respectively, more of the same precipitate could be found in the bottom POIof 9.7 and 10.8 cc. 0.1 N per 100 ('e., after 50 days, had lost tion of the glass container. practically all of the original coating of zinc, which can IF noticed in the form of a sludge occurring in the bottom of both tubes. Tube 3, after about 30 days, sliowed approximately the same volume of precipitate. Aside from the corrosion of the zinc and loss of the galvairi i n g from the cans, the presence of the insolulile sludge E,sulting from such corrosion is detrimental to high effreietiey in tlie brine t m k . This is particularly true in fixed can syntears, where excessive sludge deposits may easily lead to slow atid poor freezing at the bottom of the cans. It will be iiotcd that ncotrd brine has n much less corrosivc? efiect on galvanized iron tliaii any of those haviiig il devided alkaline reaction. This fact was not in agreeiuesit witli the ~enerallyai'ecpted assumptio~i,based 011 work done oil iron surfaces, wl.lrii:li showed that, i u gener:~l, alkaline hrines are less eorroiiw that1 those having neutral or acid reactinr1s.a Following this lead, calcium eliloride brines of varying iilhalinit.ies were used to detertiline tho efiect prodiiced on girlvaiiized surfaces. I t u%s fousid thal with 811 irnmershm of complctely galvaiiiaed strips for 30 days in 1.20 gravity solutions of c:dciurn chloride wbose alkalinities varied froin treutralitp to saturation, decided differences were very qt pnretit. Effect of Soluble Aikalinity
Carefully weighed strips of galvanized irou were diplxd once each day i i r t o B solution of eslcium chloride of 1.20 specific gravity liavitig the alkalinities shown, and allowed t.o hang exposed to the air for the remainder of t.he 24 hours. This was to get the corrosive efiect due to the air exposure. The strips were held in a hard rubber frame, which effeetually kept thein from contact with each other. At the eiid of 'J0 days the strips were cleaned with distilled water asid a stiff bristle brush until all deposits were reitloved that it was possible to get off witliout actual scraping (Table I and Plate 11).
From these results it may he seen that the effect of CUIuium brines of high alkalinity on galvaniziiig is exactly the reverse of their action upon iron as found by Poste and Donauer' and that neutral solutions have a much less corrosive action upon zinc or zinc-coated surfaces than do those of higher alkiLlinity.
*
H M ~ Siondwdi. . Ciri. 80, 14. 2nd ed
(IYLZ).
