Aug., 1 9 1 2
T H E J O U R S A L OF I - V D C S T R I A L 4.YD ELYGIaYEERINGC H E X I S T R Y .
capable of oxidizing sulfids to sulfates. Freshly precipitated, chemically pure iron sulfid and calcium carbonate were added in equal amounts in I O O cc. flasks. To each of these flasks was then added 5 cc. of Knop’s solution and after sterilization five were inoculated, the remainder being retained as checks. Within a week the inoculated solutions became cloudy, the uninoculated remaining clear. Stained amounts showed the presence of a capsulated rod showing polar staining in all inoculated flasks. This organism was present in all these flasks in practically pure cultures Comparative analyses of the contents of the check and of these flasks showed t h a t in those in which bacteria had been developed, between two and three times as much sulfate was present as in the check. The presence of this organism in the solution undoubtedly was the cause of the rapid oxidation of the sulfids which took place. However, the organism has not as yet been isolated in pure cultures and quantitative studies made of its oxidizing power. The data a t hand are sufficient to convince us that bacteria may be responsible, in part a t least, for the oxidation of sulfids to sulfates under the conditions as they exist in the sewage disposal plants here discussed. As rapidly as sulfuric acid is produced by bacteria working in and on the concrete or by atmospheric oxidation, it reacts with the calcium compounds of the cement, forming calcium sulfate. This takes up water of crystallization and swells considerably, the result being a cracking and pulverizing action and a consequent disintegration. ’ Careful search has failed to reveal any account of bacterial disintegration of concrete through the action of sulfids or sulfates. R. Grieg Smith1 investigated the disintegration of concrete in the open canals that convey the city water supply of Sidney, New South Wales. He was led to study the action of nitrifying bacteria on concrete through the work of Stutzer and Hartleb, who suggest that such forms might assist in the disintegration of the cement of water reservoirs. He concludes, however, that “there is considerable room for dou%t regarding the action of microijrganisms on cement. There is more reason to believe that the action is purely chemical.” His conclusions would seem to agree with those of Tannatt and Burke,2 who found disintegration of concrete tile to take place when iri contact with soil rich in sulfates. That even in alkali regions bacteria may have something t o do with concrete disintegration is evidenced from the work here recorded and the statement of Schreiner, Oswald and Failyers t o the effect that hydrogen sulfid is produced in the drainage waters from gypsum alkali lands and from iron pyrites. SUMMARY.
I n three of the sewage disposal plants observed, viz: Grinnell, State Inebriate Hospital, and State Hospital a t M t . Pleasant, large quantities of hydrogen sulfid are evolved. This sulfid is produced in two I.
Cent. f . Bakt., and A b f . , 8, 3 7 7 (1902). “The Effect of Alkali on Portland Cement,” Bull. Mont. Agr. Exp. Sta., 1908. 3 Bull. L?. S. Dept. 9gr., Bur. of Soils, 1906
567
ways: ( a ) by the bacterial decomposition of sulfur containing proteins and related compounds, and ( b ) by the reduction of sulfates which are contained in unusual amounts in the water supplies used. Of the two the second seems to be the more important. 2 . The organism chiefly responsible for the reduction of sulfates and evolution of hydrogen sulfid is a spiral bacterium closely related to, if not identical with, Spirillum desuljuricans. 3. The hydrogen sulfid which escapes as gas from the sewage, particularly in the dosing chamber, is partially dissolved in the moisture on the under side of the roof and concrete walls. Here i t is oxidized t o sulfuric acid partly by atmospheric oxidation and partly by bacterial action. The sulfuric acid acts upon the calcium compounds of the concrete forming calcium sulfate, and breaking down the concrete. There is often deposited an excess of free sulfur which the oxidizing agencies have not converted to sulfate. 4. The exact species of the organisms responsible . for the conversion of hydrogen sulfid into sulfuric acid have not been determined. That bacteria, however, in mixed cultures may bring aboub this change has been demonstrated. Beggiatoa and a bacillus have been isolated and are probably the most important organisms in bringing about this change. EXGINEERIXG EXPERIMENT STATION, STATECOLLEGE, AMES, IOWA.
MARKING PORCELAIN AND SILICA CRUCIBLES, ETC.l B y P. A. YODER. Received April 4, 1912. I N T R O D U CTI 0N
.
I n the analytical laboratory there often is occasion t o put upon crucibles, etc., permanent distinguishing marks which will stand ignition and mild treatment with acids and alkalis. The blue pencil or the brush and china paints which are frequently used for this purpose, the markipgs being burned in, often give results so crude as to be quite unsatisfactory, especially for articles that are before one’s eyes daily for years. Moreover, the blue-pencil marks and many china colors lack permanence, and when applied t o silica wares do not adhere satisfactorily. The writer has worked out two methods, one for marking with platinum and the other for the application of china paints, both by the use of rubber type. T H E PLATINUM PROCESS.
The crucibles are cleaned by heating for half a n hour with nitric acid, one part concentrated acid t o one part of water. A sizing is prepared consisting of a hot 5 per cent. solution of gelatin. The parts of the crucibles t o be marked are dipped into this sizing and set aside to drain and dry. When the gelatin is dry, the desired number is stamped on with a solution of platinic chlorid containing 1 2 to 1 5 per cent. of platinum-‘. e , about 32 t o 40 per cent. of the hydrated, crystallized chloroplatinic acid. The pad holding the solution may be made of six or eight folds of smooth linen or muslin and need not be much larger than the type used. This pad is nearly 1 Czrculuf 93, Bureau ol Chemistry, United States Department o Agriculture.
T H E JOURNAL OF I N D U S T R I - 4 L saturated with a few drops of the platinic chloride solution. Too much of the solution causes blurring and too little of it or too dilute a solution results in dim numbers. After the numbers are dry the crucibles are gently heated until the platinum is reduced and the gelatin burned off. This is most conveniently accomplished in a muffle. Finally, the numbers are heated for one-half minute in the flame of the blast l a m p i . e . , for one-half minute from the time it attains the temperature of the flame. If the wares are cleaned and fired as directed, the markings adhere well. The figures become more prominent if burnished by use of a china painter’s burnishing stone, if available, or of seashore sand, or less advantageously of a silica soap. The deposit is resistant t o single acids, but not to alkalis. I n some experiments library paste was substituted with good results for the gelatin sizing. Gold and mixtures of gold and platinum solutions may be applied similarly, but there is more danger of volatilizing the gold chloride before reduction takes place, and thereby causing a spreading of the deposit. The resulting figures also are less conspicuous than when platinum is used. This method of getting the deposit of platinum or gold may possibly find use also in decorating chinaware. If the solution is applied with a brush, a quill, or a glass stylus, i t may be more dilute. The same method applied to silica wares also gives very satisfactory results. APPLICATION
O F CHINA
COLORS
BY
USE
OF
RUBBER
STAMPS.
Paints mixed in oil are not satisfactory for use with rubber stamps because the type leaves on the porcelain a rim of thickened paint while the main surface of contact is relatively bare. The method finally adopted is t o stamp the wares to be marked with a sizing or varnish similar t o that which painters use for applying gold leaf. “Fat oil’’+.. e . , partly oxidized linseed oil, supplied by paint dealers-proved very satisfactory for this purpose. While this sizing is still sticky, the dry pigment is dusted on with a camel’s-hair brush. After the varnish has set, the excess of pigment is wiped off and the crucible is fired a t a strong red heat, preferably in a muffle. The “fat oil” dries slowly. This is a n advantage because then some time may be allowed between its application and the dusting on of the pigment, for the irregular layer on the porcelain t o draw out by surface tension into a smoother one. Standing over night a t room temperature, or for one hour in a drying oven a t I O O O C., suffices for the varnish t o set. The pad used for “inking” the type may consist of several thicknesses of linen cloth and is nearly saturated with this varnish. Too much varnish on the pad must be avoided, as it results in figures with ragged outlines. This varnish may readily be cleaned from the rubber type, before it has set, by use of a I O per cent. alcoholic solution of caustic potash applied with a small bristle brush. COLOR T E S T S .
Seeking a prominent color and one resistant to both
AND E-\“GI.YEERIXG
CHEIWISTRY.
Aug., 1912
acids and alkalis, a series of tests was made with samples of overglaze blues, blacks, and reds supplied by a dealer and one blue prepared by the writer. These mere stamped onto porcelain crucibles as above described. The heat used in firing was a red heat slightly lower than that a t which the colored figures on the white background disappeared (the radiation plus reflection from a colored surface equaling t h a t from a white surface). I n one test they were brought from a dull red t o the above temperature during the course of one hour and then cooled. This sufficed to make the blacks and the reds resistant to nitric acid ( 3 5 per cent.) and t o sodium hydroxide solution (IO per cent.), but the blues were appreciably soluble in the acid. To make the blues resistant, they had to be fired to a higher temperature or held a t the above maximum temperature for about an hour. To test the permanence of the markings, the acid and the alkali were each applied five minutes cold, followed by five minutes a t a boiling temperature. Of the seven blacks tried, two-uiz., a lettering black and a blue black-gave especially good effects in that they yielded a very strong black. Of the same samples when applied to silica dishes and fired as indicated, both the blacks and the reds were again resistant t o both nitric acid and alkali, but the blues, even when fired more strongly, came off very readily in nitric acid. I n these tests an electric muffle was used. I n heating porcelain crucibles to a high temperature in gas muffles in which the muffle chambers were not thoroughly sealed off from the gas chambers, and occasionally also in the electric muffle, a brown stain developed on the porcelain. This could readily be removed by heating the crucible half a minute in the blast flame, most conveniently in a suitable chimney. I n applying the rubber stamp t o the crucibles i t is difficult to avoid a sliding motion that blurs the imprint. This may be prevented by using a’ suitable guide or a steadying support. The writer found it convenient t o rest both the inverted crucible and the type holder on a smooth surface while making the impression. I n n w b e r i n g crucibles, etc., it is often advantageous to have the number on three sides so as t o make it visible, no matter which way the crucible is turned. LABOUTORY U.S. DEPARTMENT OF AGRICULTURE. WASHINGTON.
ON
THE
QUANTITATIVE ESTIMATION OF HYDROXIDE IN “BLACK LIQUOR.”
B y EDWINSUTERMEISTER AND HAROLDR . Received January 16, 1912.
SODIUM
RAFSKY.
I n the manufacture of cellulose by the soda process wood is digested under pressure with a solution of sodium hydroxide. The liquid separated from the resulting pulp is called “black liquor,” and contains the sodium hydroxide unconsumed in the reaction, together with the sodium salts of acids formed by the decomposition of the wood. A precise evaluation of this residual sodium hydroxide would give valuable information on the exact consumption of caustic soda
