Published Monthly.

Price, $5.00 per Annum. THE JOURNAL

OF THE

AMERICAN CHEMICAL SOCIETY.

VOL. XV.—NO. 4.

APRIL, 1893.

[Issued August 17, 1893.]

Members wishing extra copies of the Journal may obtain them of F. E. Dodge,

Librarian, 248 Eleventh street, Brooklyn, N. Y., at the rate of $3.00 per annum.

COMMITTEE ON PAPERS AND PUBLICATI NS: EDWARD Hart, Editor, J. H. Lonc, EpGAR F. Smrru.

CONTENTS. The Chemical and Physical Examination of Portland Cement. Thos. B. Stillman A New Weighing Apparatus.. By Dr. H. Schweitzer Note on the Use “of Eosin for Coloring Tomatoes. and W. D. Bigelow

The Electrolytic Separation of the Metals of the Second bes ® . Samuel C. Schmucker. +: sees . weeee The Action of Gases Upon Met: Blic Molybdet num én ‘Peiiiaiaten : Edgar F. Smith and Vickers Oberholtzer A New Method for the Quantitative Determination of Carbon in Iron - and yi By Otto Petterson and August Smett; translated by Geo. ‘holl PRecent Methods in Fertilizer Analysis. Edited by Edwin J. Haley- Aluminum. By R. Ll. Packard Patents of Interest to Chemists.

r

Erratum

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Council. Members ex-officio: H. W. Wiley, Pres., Albert C: Hale, Gen. Sec., Edward Hart, Editor. Term eapires Dec. 1893 - J. H. Appleton, Brown University, Providence, R. I.; C. E. Munroe, Columbian Uni- versity, Washington, D. C.; C.F. Chandler, School of Mines, Columbia College, N. Y.; T. G. Wormley, University of Pennsylvania, Phila., Pa. Term expires Dec. 1894: G. F. Barker, 3909 Locust st., Phila., Pa.; Alfred Springer, 46-50 E. 2d st., Cincinnati, O.; F. W. Clarke, Chief Chemist U. S. Geol. Surv., Washington, D. C.; C. B. Dudley, Altoona, Pa. Term expires Dec. 1895: G. C. Caldwell, Ithaca, N. Y.; J. W. Mallet, Univ. of Virginia, Charlotteville, Va.; T.H. Norton, Cincinnati Univ., Cincinnati, O.; A. B. Prescott, Univ. of Mich., Ann Arbor, Mich.

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oth and Race sts., Cincinnati, O. Mew York Section: A. H. Sabin,

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we wesw eh he we Mw IY

VoL. XV. APRIL, 1893. No. 4.

Issued August, 1893.

THE JOURNAL

OF THE

AMERICAN CHEMICAL SOCIETY.

THE CHEMICAL AND PHYSICAL EXAMINATION OF PORTLAND CETFIENT.

By THOS. B. STILLMAN, PH.D.

HE enlarged consumption of Portland cement in this coun- ij try during the past few years has caused the subject of its chemical and physical properties to receive increased considera- tion. Not only has the consumer been directly interested, that the cements used should stand specified tests, but the attention of the manufacturer has been drawn in the same direction, result- ing in improvements in methods of production.

While the Portland cement manufacture here is yet in its infancy, with a history of practically less than ten years, its product for 1891 reached a total of 450,000 barrels out of 3,500,000 barrels consumed in this country during that year. This ratio between home production and importation should be radically changed in the near future, since the product for 1892 was over 600,000 barrels. A number of causes have prevented the use of American Portland cements in the home market, one of the chief being that the imported German cements always gave higher physical tests when made by the German methods of testing than the American cements under the Ameri- can system of testing. There are a number of American Port-

7725-93

182 PORTLAND CEMENT.

land cements fully as good as the best German cements, and have shown fully as high tensile strength when tested by the same methods.

These differences in results are not due entirely to the cements, but rather to the methods in use in the different countries for testing them, for Portland cements cannot vary much in their chemical composition without losing their value.

The limit of variation is as follows :

BAO cnasisic tae cael 58 to 67 per cent.! SIO) 6 <snseweneaeiecses 20: teeb - Al1,Og «2 20eeceeeee cece 5 toto " FELOg. oe soescle cvicwns 2 fo 6% . # MgO .nceeecccsceceee 0.5 to 3 sie SOg- 200 cece cccccs cece oO5ito 25

After manufacture it is practically Ca,SiO,, and is quite dis- tinct from another product made and largely consumed here called ‘‘ hydraulic cement.”’

Experience has shown that Portland cements containing over two per cent. of magnesia (MgO) are inferior in lasting quali- ties, and by the gradual absorption of water produce cracking and disintegration (Compt. Rend., May, 1886).

Calcium carbonate (CaCO,), formed by the absorption of CO, by the CaO in the cement after manufacture, is another injur- ious compound found in cements containing more CaO than sufficient to unite with the silica to form the tri-silicate of lime. This carbonate of lime gradually produces seams and fractures after the setting of the cement. The ‘‘ Ecole Nationale,’’ of Paris, rejects all cements containing over 1.5 per cent. of sulphuric acid. Thus, if upon chemical analysis, magnesia is found present in amount over two per cent., carbonic and sulphuric acids in amounts over one and one-half per cent., the cement can be con- demned at once without any mechanical tests. ‘Therefore, it is evi- dent that a careful test of a Portland cement requires: (1) a chemical analysis to determine the proportion of the ingredients and (2) the mechaiical or physical tests to determine fineness, tensile strength, and resistance to crushing.

1K. Candlot, Etude pratique sur le Ciment de Portland (Paris, 1886).

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PORTLAND CEMENT. 183

RESUME. Per cent

§ PREP PEPEETRT RCO E Cee oe re ee ae. 24.20 AL. 2002 és teeter eraure eeeswece ds 6.22 Fe,( Sr ea ge econ einai we: ac eiatnry ate Wacelieaas tearmk anh ae 3.00 COG: 0 cvcun ss neue ab deeeieds Cemeuaneaaenaed 62.67 MgO Vise Cen wees SOON ORE CR Cem ew awed ewes 22 SS | er are ee en rr rr ey er pe 1.10 EOD ic orice dave naekemee cine eee ame eae 0.86 SO, occcee coccccccccce cess cece cess cvcccces 0.67

TOG 6006. cceccinnntnn tenes ven teens 99.94

The following well known brands of Portland cements were analyzed in my laboratory by above method.

Burham’s. Dyckerhoff’s. Saylor’s.

SiO, +++++--eee- 21.70 per cent. 19.05 per cent. 21.2 5 per: ont, Al,Oy+seeee cree 6.82 7.90 S cou Fe,O, -eeeeeeees 2:37 5.38 ee 8.25 BS 1S ERE 62.26 63.62 . 61.25 = MgO .....--.-- 1.48 ae 1.87 1.50 _ K,O..eceecceeee 1.84 a 0.88 i 1.01 aS Na,O ..+- eeeeee 0.98 66 0.36 ae 0.99 as SO, .c ee cece eens 1.20 66 0.94 se 1.38 66 MeN 6 newed viene at 1.30 es ches

99.95 se 100.00 - 99.84

In some cements quartz is a constituent in amounts varying from 0.5 to 6 per cent. It can be separated from combined silica by the method of Fresenius (Quant. Chem. Anal., p. 259).

Where carbonic acid has been indicated by the qualitative analysis the quantitative analysis should be made upon at least eight grams of the cement.

The carbonic acid rarely reaches one per cent., and while it is generally absent in well-burned cements, it is by no means an uncommon constituent to the amount of 0.15-0.30 per cent., as the following table of analyses of German cements will show'

I 2 3 4 5 6 7 8

BHO! caiden acs 61.99 62.89 63.71 63.27 65.59 59.96 64.51 60.81 Bis +0:0:6.4,00 23.69 22.80 25.37 19,80 22.85: 23.70 22.38 22.63 Fe,O,-.----- 2.71 3-40 3-14 3-22 2.76 3-15 24 2.42 BLO, scccee 8.29 7.70 4.31 6.73 5-51 8.20 9.45 7.06 MgO .....-- 0.47 1.20 1.25 2.02 1.24 1.00 2.89 Alkalies ..- 0.95 1.30 oO. nap 1.48 0.92 1.05 sees 2.83 ee 0.69 0.71 ».87 1.08 1.69 0.88 1.44 0.47 i ¢ike en en 0.27 ewes “sme 0.23 aes 0.26 0.33 Insoluble -- 0.44 reer ae 1.38 aes s 0.80

' Der Portland-cement und seine Anwendungen im Bauwesen, Berlin, 1892, p. 18.

184 PORTLAND CEMENT.

THE MECHANICAL TESTING.

The method recommended for use in this country by the American Society of Civil Engineers is as follows:

(1) Determination of fineness.

(2) Liability to checking or cracking.

(3) Tensile strength.

Fineness.—Tests should be made upon cements that have passed through a No. 100 sieve (10,000 meshes to the square inch), made of No. 40 wire, Stubb’s wire gauge. The finer the cement the more sand it will unite with and the greater its value.

Liability to Checking or Cracking.—Make two cakes of neat cement two or three inches in diameter, about one-half inch thick, with thin edges. Note the time in minutes that these cakes, when mixed with mortar to the consistency of a stiff, plastic mortar, take to set hard enough to stand the wire test recommended by General Gillmore, one-twelfth inch diameter wire loaded with one-fourth pound, and one twenty-fourth inch diameter wire loaded with one pound.

One of these cakes, when hard enough, should be put in water and examined from day to day to see if it becomes contorted or if cracks show themselves at the edges. such contortions or cracks indicating that the cement is unfit for use at that time. In some cases the tendency to crack, if caused by too much lime, will disappear with age. The remaining cake should be kept in the air and its color observed, which, for a good cement, should be uniform throughout.

Tensile Strength.—One part of the cement mixed with three parts of sand for the seven days and upward test, in addition to the trials of the neat cement. The proportions of cement, sand, and water should be carefully determined by weight, the sand and cement mixed dry, and all the water added at once. The mixing must be rapid and thorough, and the mortar, which should be stiff and plastic, should be firmly pressed into the molds with the trowel without ramming and struck off level, the molds in each instance, while being charged and manipu- lated, to be laid directly on glass, slate, or other non-absorbent material. The molding must be completed before incipient

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PORTLAND CEMENT. 185

setting begins. As soon as the briquettes are hard enough to bear it, they should be taken from the molds and kept covered with a damp cloth until they are immersed. For the sake of uniformity, the briquettes, both of neat cement and those con- taining sand, should be immersed in water at the end of twenty- four hours, except in the case of one day tests. Ordinary clean water having a temperature between 60° F. and 70° F. should be used for the water of mixture and immersion of sample. The proportion of water required is approximately as follows:

For briquettes of neat cement, about twenty-five per cent.

For briquettes of one part cement, one part sand, about fifteen per cent. of total weight of cement and sand.

For briquettes one part cement, three parts sand, about twelve per cent. of total weight of cement and sand.

The object is to produce the plasticity of rather stiff plasterer’s cement.

An average of five briquettes may be made for each test, only those breaking at the smallest section to be taken. The bri- quettes should always be put in the testing machine and broken immediately after being taken out of the water, and the tem- perature of the briquettes and of the testing room should be con- stant between 60° F. and 70° F.

The following table shows the average minimum and maxi- mum tensile strength per square inch which some good cements have attained. Within the limits given the value of a cement varies closely with the tensile strength when tested with the full dose of sand.

AMERICAN AND FOREIGN PORTLAND CEMENTS.—NEAT. I Day (1 hour, or until set, in air, the rest of the 24 hours in water)..-

cece cece ee cece ee ce cccscccees -+++-+-from 100 to 140 lbs. per square inch 1 Week (1 day in air, 6 days in water )-.-from 250 to 550 lbs. per square inch I Month, 28 days (1 day in air, 27 days in water).--+++--++eeeeee eee

olgansis dading se nwa iewa teen ce gemenee from 350 to 700 lbs. per square inch 1 Year (1 day in air, the remainder in water) --++.+--+ee cece cece eens

pelilaidel Nasieieuheneiax soise spain sa aeens from 450 to 800 lbs. per square inch AMERICAN AND FOREIGN PORTLAND CEMENTS.—I PART OF CEMENT TO

3 PARTS OF SAND.

1 Week (1 day in air, 6 days in water.-from 80 to 125 lbs. per square inch 1 Month, 28 days (1 day in air, 27 days im water)-+--+-+++-+eeeeee cree

ds GN ha Reed a AaaEaE Od eke sae -+-++from 100 to 200 lbs. per square inch

186 PORTLAND CEMENT.

1 Year (1 day in air, the remainder in water).-.-...-..... ee cceccccene SE CE, CC OE I OT from 200 to 350 lbs.’ per square inch

The machines for determining the tensile strength of Portland cements in use in this country are the ‘‘ Fairbanks,’’ Fig. 1, and the ‘‘ Riehle,’’ Fig. 2.

camer

FIG. 1.

The Fairbanks machine is automatic and is operated as fol- lows:

Hang the cup on the end of the beam; see that the poise is at the zero mark and balance the beam by turning the ball. Place the shot in the hopper. Place the briquette in the clamps and adjust the hand wheel so that the graduated beam will be inclined upward about 45°. Open the automatic valve so as to allow the shot to run slowly. When the specimen breaks the beam drops and closes the valve through which the shot has been pouring. Remove the cup with the shot in it and hang the counterpoise weight in its place. Hang the cup on the

1In regard to modification of these conditions required for tensile strength, consult Transactions American Society of Civil Engineers, August 1891, p. 285.

ol-

is

Ips be

the 1as ing the

sult

PORTLAND CEMENT. 187

hook under the large balance ball and proceed to weigh the shot, using the poise on the graduated beam, and the weights on the counterpoise weight. The result will show the number of pounds required to break the specimen.

‘he en _] =a aw

Wah

ay MCT TTT TTT TT TTT TTT TTT Te TT TT TT |

FIG. 2.

The ‘‘ Riehle,’’ while not automatic, is accurate, and responds to differences as slight as 1 pound in 2,000. The distinctive features are:

(a) The poise moves quietly and smoothly on the weighing beam.

(6) The weighing beam is long and the marks not too close together. The slightest movement of the beam is promptly and plainly observed by the motion of the indicator.

(c) The levers are tested and sealed to U.S. standard weight.

(d) The arrangement of the ‘‘grips’’ to hold the briquettes is such that they are always swung from pins, thus giving the test upon the cement when the briquette is on a dead straight line.

188 PORTLAND CEMENT.

Directions for Testing Portland Cement According to the Official German Rules'.—The quality of a mortar made with cement depends not only on the strength of the cement itself, but also on the degree of sub-division of the same. It is therefore neces- sary to make the tests both with neat cement and with a mixture of the same with ‘‘standard sand.’’ ‘This latter as used at the Royal Testing Station at Berlin, is produced by washing and drying quartz sand, which must be clean as possible, and after- wards be sifted through a sieve of sixty meshes per square centimeter (387 meshes per square inch), by which process the coarsest particles are separated. The sand is again sifted through a sieve having 120 meshes to the square centimeter (774 meshes per square inch). ‘The residue remaining in this sieve is the standard sand for experiments, the coarsest and finest particles having been eliminated. It is absolutely neces- sary in order to obtain uniform results to use only the ‘‘ standard sand,’’ as the size of the grain has a material influence on the re- sults of the testing. The sand must be clean and dry, and all earthy aud other substances previously removed by washing.

Preparation of Briquettes of Neat Portland Cement.—Upon a slab of metal or marble are laid five sheets of filtering paper, which have been previously saturated with water, and upon these are placed five brass molds (Fig. 3) thoroughly clean and moistened with water. One thousand grams of cement and 250 grams of water must be thoroughly mixed, well worked up, and when the resulting mass has been rendered perfectly homogen- ous, it is poured into the molds. The latter must be gently tapped by means of a wooden hammer with equal force on both sides during ten to fifteen minutes to insure the escape of confined globules of air. The molds must be carefully filled up until the mass becomes plastic, the superfluous mortar is then struck off, and the mold carefully withdrawn. The samples, after remaining twenty-four hours exposed to the air, at a temperature of about 60° F., must be immersed in water having the same temperature, and care must be taken that they remain covered with water until the

Fie. 3.

+ Portland Cement, by Gustav Grawitz.

he

PORTLAND CEMENT. 189

time arrives for breaking them. In order to obtain a proper average at least ten briquettes should be prepared for every examination.

Preparation of Briquettes from a Mixture of Portland Cement and Standard Sand.—Place the molds on metal as described in preparation of neat cement briquettes. The quantities (by weight) specified of cement and sand are thoroughly mixed and to this is added the requisite quantity of water. The whole mass is then worked up with a trowel or spatula until it becomes uniform. In this manner is obtained a very stiff mortar. The

molds are filled and mortar heaped up. The latter is then beaten into the molds with an iron trowel, at first lightly, and afterwards more heavily, until it becomes elastic and water ap-

pears on the surface. The superfluous mortar is then scraped off with a knife and by means of the same the surface is leveled. The further treatment of these briquettes is the same as for neat cement briquettes. The average of ten breaking weights furnishes the strength of the mortar tested.

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I'he machine in general use in Germany for determining the tensile strength of cements is the Michaelis (Fig. 4), and from

A NEW WEIGHING APPARATUS.

190

this is derived, with modifications, the ‘‘ Reid and Bailey”’ machine in use in England, and the ‘‘ Fairbanks’’ previously

described. [TO BE CONTINUED. ]

A NEW WEIGHING APPARATUS.

By Dr. H. SCHWEITZER. Read before the New York Section May 29, 1893.

HE weighing of liquids for analytical purposes has always been very tedious, and many forms of apparatus have been devised for facilitating this operation. But all of them had— disadvantages. The distinguishing feature of our ‘‘ Weighing Pipette,’’ which was constructed with the help of our assistant, Mr. E. Lungwitz, is that it consists of a single piece without any cock or other complicated parts.

The weighing pipette presents the general appearance of a bulb pipette. Where the suction tube joins the bulb there is a short capillary tube which projects towards the wall of the bulb, the opposite wall being flattened to furnish a firm rest for the pipette on the scale. saad pipettes are constructed with either large or small apertures of the de- livery tube, according to the physical properties of the substance to be weighed. For light liquids, acids, and oils we use small aper- tures; for milk, syrups, heavy oils, and fats we take pipettes with large apertures.

By capillarity and suction the liquid runs back into the delivery tube without any losses. For ex- ample, we weighed a quantity of fuming sulphuric acid in a pipette with small aperture, and after half an hour no change in the weight of the pipette was perceptible. A short delivery tube cannot be used as there is danger of the liquids running back on the outside of the tube, thereby dripping on the scales.

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USE OF EOSIN FOR COLORING TOMATOES. IOI

The pipettes can be warmed directly in the flame without danger of breaking them, in case the weighed substarice solidi- fies in the bulb (lard, etc).

On account of the small surface of the bulb in the little pipettes, the error in weighing slightly warmed liquids can be neglected for all practical purposes.

The inside capillary tube must be turned up as much as pos- sible to gain space. The capillary must have a very small aper- ture to allow dropping and prevent liquid from entering the suction tube. The apparatus can be easily cleaned by drawing benzene or hot soda solution, etc., through it, then alcohol and ether, and drying it in a current of air.

The weighing pipette is made in different sizes with bulbs from five cc. to 100 cc., ete., etc., and is sold by E. Greiner, 146 and 148 William street, New York City.

LABORATORY OF BREYER & SCHWEITZER, 159 FRONT ST., NEW YORK CITY.

[CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF THE U.S DEPARTMENT OF AGRICULTURE, SENT BY H. W. WILEY.—NO. 7.] NOTE ON THE USE OF EOSIN FOR COLORING TOPIATOES. By K. P. MCELROY AND W. D. BIGELOW.

Received June 22.

OME time since, in accordance with the instructions of Dr.

Wiley, a qualitative examination was made of a sample of tomato color made by a Cincinnati firm and sent to the Depart- ment of Agriculture by Mr. H. E. Taylor, of Brooklyn.

The sample was in a small bottle bearing the label, ‘‘ tomato color.’’ It consisted of a thin red liquid, showing a strong fluorescence when diluted. Treated with hydrochloric acid a flocky orange precipitate was obtained and the liquid after fil- tration showed no color, even when made alkaline. The precipi- tate was freely soluble in alkalies with which it reproduced a red liquid resembling the original. It was also freely soluble in ether, giving a pale yellow solution. A portion of the sample was mixed with lime, evaporated to dryness, and burnt till white. A water solution of the resulting mixture of ash and

192 USE OF EOSIN FOR COLORING TOMATOES.

lime after acidifying with nitric acid, gave a heavy precipitate with silver nitrate. Another portion of the solution treated with bleaching powder and hydrochloric acid liberated a substance which was taken up by chloroform, imparting to it a strong yellow color. A portion of the original sample was reduced with sodium amalgam and to the resulting nearly colorless liquid a drop or two of dilute permanganate solution added. A liquid having a deep green fluorescence resulted. The fluores- cence was so strong that the liquid was nearly opaque. In view of the reactions cited, the substance under examination was pronounced to be an aqueous solution of brom-eosin (tetra- bromfluorescein).

Eosin is one of the most extensively used of the so-called anilin colors. The statement has been made that it is sometimes employed in coloring candy, and more rarely, other articles of food. Its use for coloring tomatoes, however, has never been published to our knowledge. It is well adapted for this purpose inasmuch as in a very dilute state it possesses a yellow color not unlike that of the liquor which surrounds canned tomatoes. Addition of a single drop of the solution examined to the liquid contents of a can of tomatoes was found to hardly change the color at all, but to cause a marked change for the better in appearance.

At the suggestion of Dr. Wiley an effort was made to work out a method by which brom-eosin could be discovered when added to canned tomatoes. The readiest foundation for such a method appeared to be the fact that eosin can be readily ab- stracted from acidified aqueous solutions by ether, and that from this ether solution it in turn can be withdrawn by dilute alkali. The solution so obtained has a characteristic fluor- escence.

A large tomato was taken, mashed, and water added. The mixture was divided into two parts and to one a drop of the tomato color added. Both portions were then placed in dishes on the water bath and heated for three hours, replacing the evaporated water from time to time. At the expiration of this time the liquid part was strained off from each portion through cotton bags. The volumes obtained in each case measured

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USE OF EOSIN FOR COLORING TOMATOES. 193

about 150 cc. They were acidified with hydrochloric acid, placed in separatory funnels, and shaken with ether. The aqueous portion of the liquid was then drawn off and the ethereal solution washed with water. After separating from this wash water, twenty cc. of dilute solution of caustic soda were placed in each funnel and the shaking repeated. The alkaline liquid in one funnel then showed a strong yellow- green fluorescence. The color was almost exactly as intense as that produced in a similar amount of the dilute alkali by a drop of the tomato color. This was the quantity used. On once more shaking the ether remaining in the separatory funnel with alkali an aqueous solution was obtained showing a barely per- ceptible fluorescence. From this it was evident that the first portion of alkali had extracted practically all of the coloring matter. From the other portion of tomato, the one to which no coloring matter had been added, the alkaline liquid obtained had a slight yellow color, but showed no fluorescence.

A can of tomatoes was next procured, opened, the contents strained in a bag, and the resulting liquid divided into two parts. To one portion a drop of the eosin solution was added. Both portions were then acidulated and extracted with ether. The ether extract in both cases assumed a light yellow color. The ethereal solutions were washed with water several times and then shaken with dilute alkali. Both alkaline solutions were dark colored. Neither showed fluorescence. The ether retained some color. This, of course, was not due to eosin, which, as was just shown, is quantitatively extracted from ethereal solution by alkali. The alkaline liquids were acidified and once more extracted, using fresh ether. Nearly all the coloring matter in the acid liquid was extracted by the ether. After washing the ethereal liquids with water several times they were shaken with more alkali. The resulting solution in one case showed a faint and badly-defined fluorescence. ‘The color of the liquid was too dark, however, to permit any certain recognition of the phenomenon. The ether was not wholly decolorized. It was thrown away, and the two aqueous solu- tions acidified and extracted with fresh ether. ‘The new ethereal solutions after washing with water gave with alkalies a light

194 USE OF EOSIN FOR COLORING TOMATOES.

colored solution, which in one case was unmistakably fluor- escent. In the other sample no fluorescence whatever was per- ceptible. It was therefore evident that the presence of eosin could be recognized with certainty in the presence of the natural coloring matter of the tomato even when existing in but small quantity.

Other experiments were made in which larger quantities of the tomato color were used—two, three, and four drops to 300 ce. of tomato juice. In every case recognition was positive. Asa rule one or two extractions were sufficient to allow the fluor- escence of the eosin to be easily recognized. ‘Trials were made of the fluorescein reaction proposed by Baeyer' for the recogni- tion of eosin to see if it offered any advantage, but such was not found to be the case. The test for brom-eosin, of which the sample under examination consisted, is sufficiently delicate and characteristic to render further complication unnecessary. If iod-eosin were used by the canner instead of brom-eosin it might then be necessary to resort to Baeyer’s test, for iod-eosin does not fluoresce and the color is not sufficiently distinctive to per- mit its recognition. Iod-eosin, however, is higher in price and not so well adapted for use in canned tomatoes, for a slight fluorescence is rather desirable in this case.

To recapitulate, the method we propose for recognizing the presence of brom-eosin in canned tomatoes is to strain off the solid matter and to the juice add hydrochloric acid and ex- tract with ether. The ethereal solution is to be washed and shaken up with dilute solution of caustic soda. Should this solution be strongly colored, it is to be acidified and extracted with ether, the ether shaken up with dilute alkali and the alter- nate extractions with ether and alkali repeated till the presence or absence of eosin is demonstrated. The natural coloring mat- ter of the tomato is not completely separated from acid solution by ether, nor is it completely abstracted from ether by alkali, so that by repeating the process sufficiently often it is separated to an extent sufficient to permit the recognition of eosin. Eosin is extracted quantitatively in both cases. Should it be desired to apply Baeyer’s method in any case in which the presence of iod-eosin may be