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T H E J O U R N A L OF I N D U S T R I A L A N D EA’GINEERING C H E M I S T R Y .
the least effective as a preservative. I n case of cinnamic aldehyde a concentration of 2 parts per 10,000 was sufficient t o inhibit the growth of most organisms, only two out of the nine employed showing growth a t this concentration, With eugenol 5 parts per 10,000proved insufficient to prevent the growth of all the organisms tried, four out of nine having grown. Benzoic acid on the other hand revealed a much weaker antiseptic action than either of the above, eight forms out of nine growing in a concentration equivalent to I O parts per 10,000, and five out of nine in a concentration of 2 0 parts per 10,000, while three others showed doubtful evidence of growth. In view of the fact that this work on pure cultures was performed by one of the authors, whereas the work on the apple sauce was performed independently by the other, it is interesting to note that the results in both cases coincide remarkably with one another. For direct contamination of the specially prepared apple sauce, it was found that 0.01 gram of cinnamic aldehyde per I O O grams of sauce (equivalent to I part per 10,000) was sufficient t o delay growth a t least 60 days and that 2 parts per 10,000prevented all growth, results with which the data in Tables VI and VI1 correspond very closely. With eugenol the same remarkable coincidence maintains, the results of both observers showing that I O parts per 10,000 were sufficient to inhibit growth. Thus, both methods, the more practical household method of direct exposure to contamination, as well as the laboratory pureculture method, yielded identical results in all respects. I n view of the above, it appears that cinnamic aldehyde and eugenol as such possess, considerable preservative action and aid materially in preserving substances to which they are added. Both are contained in such spices as cinnamon and cloves. N o doubt the marked preservative action of these spices, as shown in the above experiments, must be attributed t o their content of these essential oils. As this preservative action takes place, even when the spices are used in the small quantities necessary for flavoring, their use can be recommended in contrast to such spices as pepper and ginger which have been shown t o possess but little, if any, preservative action. The more liberal use of cinnamon and cloves in the preparation of ketchup may perhaps remove the necessity of adding sodium benzoate for preserving it, a practice to which there is so much objection. AGRICULTURAL BACTERIOLOGICAL LABORATORIES, UXIVERSIWOF WISCONSIN, MADISON.
______ THE DETERMINATION OF GLIADIN OR ALCOHOL-SOLUBLE PROTEIN IN WHEAT FLOUR. B y RALPHHOAGLAND. Received July 28, 1911.
O s b m e I ’ in his monograph, “The Proteins of the Wheat Kernel,” states that the following proteins .are present in the wheat kernel: “Gliadin insoluble 1 Proteins of
f k e Wheal Kernel, pub. by Carnegie Inst., 1907.
S o v , 191I
in neutral aqueous solutions, but dist‘inguished from all others by its ready solubility in 7 0 per cent. alcohol; glutinin, a protein having a similar elementary composition to gliadin, soluble in dilute acid and alkaline solutions, and yielding a wholly different proportion of decomposition products when boiled with strong acids ; leucosin, an albumin-like protein, freely soluble in pure water, and coagulated b y heating its solution t o jo-60 C. ; a globulin, similar in composition and properties to many globulins found in other seeds, and one or more proteoses which are present in very small quantity.” Osborne states that globulin, albumin and proteose are the proteins found in the embryo of the wheat kernel, while the endosperm consists nearly entirely of gliadin and glutinin. The latter part of this statement of Osborne’s is hardly correct, since wheat flour contains considerable proteid material-globulin, albumin and proteose, soluble in dilute salt solution -usually amounting to 10-15 per cent. of the total protein.‘ However, the proteins of the wheat endosperm do consist very largely of gliadin and glutinin. The quantitative separation of the proteins of wheat flour is very difficult and not possible of absolute accuracy, since no one protein is entirely insoluble in the solvent used t o extract another protein. Thus while a I O per cent. sodium chloride solution will extract albumin, globulin and proteoses, yet it will also extract some gliadin. Likewise, 7 0 per cent. alcohol, while presumably extracting only gliadin, also extracts some albumin, globulin, etc. Chamberlain2 has done a large amount of work in the quantitative separation of proteins of wheat flour. In his latest report, Journal of the American Chemical Society, 1906, he makes, among others, the following conclusions: “As recommended by the author in the Association of Official Agricultural Chemists, the separation of the proteins of wheat into more than two groups, niz,, first, alcohol-soluble, second, alcoholinsoluble, seems unwarranted, both because of the difficulty of making a further quantitative separation, and because of the indefinite value of such separation. In the light of all data available to the writer, this statement of Chamberlain’s seems wholly justified, I t is to be hoped, however, that methods may be devised by which an accurate quantitative separation of the wheat proteins may be accomplished. A large amount of chemical investigation has been conducted during the past ten years with wheat flour, and one of the chief objects in this work has been to determine some relation between the composition of the flour and its strength, i. e . , ability to produce a large, well piled loaf. An immense number of gliadin determinations have been made in this work, to ascertain if any relation existed between the ration of gliadin to the total protein, and the strength of the flour. The writer proposes t o discuss this matter in detail in a later paper. The determination of gliadin, or to be scientifically See Chamberlain, Bull. 90, p. 124, Bureau of Chem., U. S. Dept. of Agr. See Chamberlain, BwUs. 81 and 90, Bureau of Chem., U. S. Dept. of A g r ; also Vol. 28, No. 11, J . A m . Chem. SOC. 1 2
f
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T H E J O C R N A L OF I,I’DUSTRIAL AA’D ESGIA’EERING C H E M I S T R Y .
correct, alcohol-soluble protein in wheat flour, is simple in principle, and duplicate determinations check very closely. I t consists, as usually practised, in frequent agitation for several hours of a weighed quantity of flour with a definite volume of dilute alcohol, letting stand over night, and the final determination of nitrogen in an aliquot portion of the filtrate, As has been mentioned, a single operator can get duplicate determinations t o check very closely, and likewise different operators using exactly the same method will get closely agreeing results. Unfortunately, however, the situation is t h a t different chemists use different methods, and hence their results are in no sense comparable, unless the methods used are accurately described, when the results may be compared provided the methods are essentially the same. B u l l e t i n 107, Bureau of Chemistry, U. S . Dept. of Agr., Official and Provisional Methods of Analysis, Association of Official Agricultural Chemists, contains no method for the determination of gliadin or other wheat proteids. Page 59, Sec. VIII, “Methods f o r the A ~ i a l y s i of s Cereal Foods, is blank except for the heading. The chief differences in methods used for the determination of alcohol-soluble protein in wheat flour are these: I. I n the strength of alcohol. 2 . I n the method of extraction. What strength alcohol should be used? It is commonly recommended that 7 0 per cent. alcohol be used, but a s a rule the reader is left in doubt as to whether 7 0 per cent. alcohol means 70 per cent. b y weight or 7 0 per cent. b y volume. Seventy per cent. alcohol b y weight h a s a specific gravity of 0.8 7 2 9 and is equivalent to 76.91 per cent. alcohol by volume. Seventy per cent. alcohol b y volume has a specific gravity of 0.8898 and is equivalent to 62.45 per cent. b y weight. There is a difference of 6.91 per cent. alcohol b y volume or 7.55 per cent. alcohol by weight between alcohol of 7 0 per cent. strength b y weight and 7 0 per cent. b y volume. Provided 7 0 per cent. alcohol b y weight a n d 7 0 per cent. b y volume extracted the same amount of protein from a flour, one might as well be used as the other. I n fact, however, there is a considerable difference in the extractive power of these two strengths of alcohol, as will be shown later. Just why should 7 0 per cent. alcohol (whether b y weight or by volume) be used instead of alcohol of some other strength, anywhere from I O per cent. t o 95 per cent? Apparently 7 0 per cent. alcohol has been used on the supposition that it would extract a larger quantity of protein than alcohol of any other strength. Osborne‘ makes the following statement : “Exactly what strength of alcohol dissolves the largest proportion of gliadin has never been determined, but the maximum solubility is attained with about 7 0 per cent. of alcohol by volume.” Without doubt Osborne considers t h a t alcohol of t h a t strength which will extract the largest amount of protein should be used for the determination of gliadin in wheat flour. I n the light of all available data, it seems perfectly logical P r o f e i m o i the Wheat K c r m l , pub by Carnegie I n s t , 1910, p 109.
839
that alcohol of that strength which will extract the maximum amount of protein should be used for the determination of gliadin in wheat flour. Some chemists object t o using alcohol more dilute than 7 0 per cent. on the ground that the weaker alcohol extracts the larger proportion of non-gliadin protein, This is a weak objection, since it is a rather difficult matter t o dctermine just what strength alcohol will extract the largest amount of true gliadin a n d the smallest amount of non-gliadin protein. I t would certainly seem best t o use that strength alcohol which will extract the largest amount of total protein. A number of investigators have determined the relative amounts of protein extracted from flour b y alcohol of different strengths. ShuttI determined the amount of protein extracted from flour by alcohol varying in strength from 60 per cent. t o 7 5 per cent. by weight, with the following results: Strength of alcohol by weight. Per cent. 60 62 5 65.0 70 75
Gliadin.
Per cent.
5.36 5.30 5.24 4.71 3.41
Proportion of protein in the form of gliadin. 54.0 53.4 52.9 47.4 34.3
From this data it will be noted that there is a constant decrease in the amount of protein extracted as the alcohol increases in strength from 60 per cent. t o 75 per cent. by weight. Since 60 per cent. alcohol is the lowest strength shown there is no means of knowing just what strength of alcohol would extract the largest proportion of protein. Sixty-two and five tenths per cent. alcohol by weight corresponds closely with 7 0 per cent. by volume. By looking a t the above table it will be noted that 70 per cent. alcohol by weight extracts 0.59 per cent. less protein than 62.5 per cent. by weight, or 7 0 per cent. by volume. The gliadin number with the 7 0 per cent. alcohol b y weight is 47.4, while with 7 0 per cent. alcohol b y volume i t is 53.4. Obviously i t makes considerable difference whether alcohol used for the determination is 7 0 per cent. by weight or b y volume, or whether alcohol of some different strength is used. Shutt makes special mention of the fact that alcohol used for the determination of gliadin should be prepared with great accuracy, since, as his results show, slight differences in strength of the alcohol materially affect the amount of protein obtained. The above writer uses 7 0 per cent. alcohol by weight for the determinations reported in that bulletin. Snyder’ in his report on the separation of vegetable proteins before the Association of Official Chemists, 1906, makes reference to several investigations conducted to determine what strength of alcohol would extract the maximum amount of protein from wheat flour. Teller, of the Arkansas Station, determined the amount of protein extracted from flour b y alcohol varying in strength from 40 per cent. t o g j per cent., with the following results: Bull 117, Central Expenmental Farm, Ottawa, C a n , 1907 Bull 106, Bureau of Chem., U S. Dept. of Agr
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING C H E X I S T R Y.
840
AMOUNT OF NITROGEN DISSOLVEDBY VARYING STRENGTHS ALCOHOL. Alcohol b y volume. Per cent. 95 90 85 80 75 70
Alcohol-soluble nitrogen. Per cent. 0.21 0.31 0.61 0.89 1.08 1.18
Alcohol b y volume. Per cent. 65 60 55 50 45 40
Alcohol-soluble nitrogen Per cent. 1.30 1.38 1.40 1.40 1.40 1.40
It will be noted that the maximum extraction was obtained with 40-55 per cent. alcohol b y volume. Snyder determined the amount of protein calculated a s nitrogen extracted by alcohol, varying in strength from 60-70 per cent. b y weight, with the following results : PROTEIN
CALCULATED AS
Alcohol.
NITROGEN DISSOLVED BY 60-70 PER ALCOHOL.
Per cent. 60 68
io 72
CENT,
Nitrogen. Per cent 0.85 0.74 0.70 0.67
Shutt also reports results obtained with alcohol varying in strength from 60 to 86.4per cent. by weight, the amount of protein extracted decreasing with the increase in strength of alcohol. The results are as follows : GLIADIN NITROGEN DISSOLVED BY VARYING STRENGTHS ALCOHOL. Alcohol. Per cent. b y weight. 60 62.5 65 70
Gliadin nitrogen. Per cent. 0.94 0.93 0.92 0.83
Alcohol. Per cent. by weight.
Gliadin nitrogen. Per cent.
75 76.8 86.4
0.60 0.66 0 12
..
..
On looking over all available data, it appearsTthat Teller is the only one who has determined the solvent power of alcohol of less strength than 60 per cent. b y weight. He finds t h a t the protein extracted by alcohol varying in strength from 40-55 per cent. b y volume is practically constant. The other investigators find a gradual decrease in solvent action of alcohol as it increases in strength above 60 per cent. While Teller's work appears conclusive, it was thought worth while t o cover the ground even more fully, both as regards strength of alcohol and the method of extraction, in order t o obtain the maximum amount of gliadin from flour. The following points were investigated: I . Time necessary for maximum extraction. 2. Strength alcohol necessary for maximum extraction. 3. The effect of temperature on the determination of gliadin. The common method for the determination of:gliadin is. t o extract z grams of flour with I O O cc. neutral alcohol in a glass or rubber stoppered flask for IS t o 24 hours, shake frequently the first three t o four hours, then allow t o stand over night, filter'and determine nitrogen in a n aliquot portion of the filtrate in the usual manner. This method is undoubtedly accurate provided the flask is shaken frequently for some time. The only objection is the time element. In commercial laboratories, where immediate results
SOV., T 9i I
are wanted, time is a n element of considerable importance. This laboratory is provided with a soil shaker used for the mechanical .analysis of soils. It has compartments for 16 8-ounce milk sterilizer bottles, has a backward and forward. movement, and is run by a I / , h. p. motor. The following experiment was conducted with macaroni flour to determine the length of time necessary, with constant shaking, to affect a complete extraction of gliadin from flour, Approximately 5 grams of flour were weighed into each of five sterilizerbottles; zoo cc. neutral 7 0 per cent. alcohol b y weight added. Four bottles were placed in the shaker, and shaken for periods of 30, 45, 60 and 90 minutes respectively. The fifth bottle was shaken by hand a t intervals for three hours, and then let stand over two days, making forty-seven hours in all. I n the Gase of samples run in the shaker, filtration was facilitated by running the samples for ten minutes in a n electric centrifuge, which gave a clear solution which hardly needed filtering. Nitrogen was determined in filtrate b y the modified Kjeldahl method. GLIADINEXTRACTED O N SHAKING
FOR
DIFFERENT PERIODS. Per cent. gliadin N extracted.
Sample.
Time shaken.
1
30 min.
0.90
2
45 min. 60 min. 90 min. Shook frequently for 3 hrs., let stand 44 hrs.
0.95 0.96 1.03 0.97
3 4 5
A similar test was run with a sample of soft winter wheat flour, using 7 0 per cent. alcohol by weight, with the following results : Sample. 1 2 3
Time shaken. 60 min. 90 min. Shook frequently for 3 hrs.,let stand 15 hrs.
Per ceni. gliadin N extracted. 0.89 0.90 0.84
I n the first test, shaking for go minutes gives slightly higher results than shaking for 60 minutes. Shaking for 60 minutes gives practically identical results with the method (No. 5 ) where the sample is shaken for 3 hours and let stand over night or longer. In test No. z practically identical results are obtained where samples are shaken for 60 and 90 minutes respectively. Sample No. 3, using the old method, gives slightly lower results than the first two samples. These tests show that alcohol-soluble protein can be as completely extracted from flour b y shaking the sample vigorously for 60-90 minutes in a shaking machine, as when the sample is shaken frequently for two t o three hours b y hand, and then let stand IS hours more or less. The method now in use in this laboratory fcr the determination of alcohol-soluble protein in flour is as follows: weigh approximately 2 grams of flour into an 8-ounce milk sterilizer bottle, add I O O cc. neutral 5 0 per cent. b y weight alcohol; shake in machine for one hour, centrifuge for ten minutes, filter, determine nitrogen in aliquot portion of filtrate b y modified Kjeldahl method. Correction is always made for a
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T H E J O U R N A L OF I N D U S T R I A L AAVD ENGILVEERIAYGC H E M I S T R Y .
blank determination run with the alcohol, etc. I n using a shaking machine it is, of course, necessary t o have the bottles shaken vigorously so that the flour will remain in suspension. The use of the centrifuge makes filtration easy, which would otherwise be rather slow, due to fine flour particles in suspension. I n making up the varying strengths of alcohol reported in this paper, the alcohol table found in Leach was used, and the specific gravity was determined by means of a Sartorius balance. The making u p of a definite strength alcohol for the determination of gliadin is a matter of considerable importance. An accurate Westphal or Sartorius balance, or picnometer, should be used, and not a spindle. The temperature a t which the reading is taken should of course be exactly that for which the alcohol table is intended.
all extractions are carried on under exactly the same conditions, extraction with hot alcohol probably will not give as accurate results as our present methods. AMOUiST
OF
PROTEIX
EXTRACTED
FROM
FLOUR
WITH
ALCOHOL O F V A R Y I N G D E G R E E O F STRENGTH.
The following table reports results of tests run t o determine the relative solvent action on wheat protein, of alcohol varying in strength form I O per cent. to 7 5 per cent. by weight; and including one extraction with distilled water. The method used for all determinations is the one previously described as being used in this laboratory, all tests being run under exactly the same conditions except as regards strength of alcohol. RELATIVEEXTRACTIVEPOWEROF ALCOHOL OF VARYING STRENGTHS.
Alcohol by weight. Per cent. Water.
T H E EFFECT O F T E M P E R A T U R E O N T H E E X T R A C T I O N O F G L I A D I N F R O M FLOUR.
Opinion differs as t o the relative solvent action of cold or boiling alcohol on flour. Leach1 gives a method for the determination of gliadin which consists in shaking I gram of flour with I O O cc. 7 5 per cent. hot alcohol, and keeping the mixture a t a temperature just below the boiling point of the alcohol for one hour, shaking frequently. The mixture is then filtered and nitrogen determined in the usual way. Chamberlains reports results showing that cold alcohol extracts more gliadin from flour than hot alcohol. The following tables show the results of a test conducted in this laboratory t o determine the amount of protein extracted b y 50 per cent. b y weight alcohol a t different temperatures. Approximately z grams of flour were weighed into each flask, I O O cc. of cold 50 per cent. b y weight alcohol added, single tube condensers inserted and each flask placed in a water bath a t the desired temperature. Samples were shaken frequently during the period of extraction, and were finally allowed to cool before filtering. A baker’s patent spring wheat flour was used.
841
10 20 30 35 40 45 50 55 60 65 70 75
Hard Spring Baker’s *tent. Per cent. gliadin nitrogen. 0.60 0.56 0.57 0.99 1.13 1.16 1.17 1.18 1.13 1.12 0.96 0.90 0.61
Soft Winter patent. Per cent. gliadin nitrogen. 0.51
0.46 0.50 0.78 0.92 0.93 1.02 1.03 0.99 0.96 0.87 0.87 0.54
.From this table it will be noted t h a t alcohol of per cent. strength extracts less protein than distilled water, and t h a t as alcohol increases in strength from I O per cent. to 50 per cent., i t extracts more protein. Alcohol varying in strength from 45 per cent. t o 55 per cent. extracts practically the same amount of protein. As the alcohol increases in strength from 55 per cent. t o 7 5 per cent. its solvent action decreases, the drop being more rapid as the alcohol increases in strength. Seventy-five per cent. alcohol extracts about the same amount of protein as distilled water. The results of this work confirm the work of Teller, who found t h a t alcohol of from 40 per cent. to 60 per cent. by volume extracted the most protein from TEST NO 1 wheat flour, and there appears to be no logical reason Per cent. why alcohol of 7 0 per cent., whether b y weight or of gliadin Sample volume, should be used for the determination of nitrogen. No. Temperature. Period of extraction. gliadin, or alcohol-soluble protein in wheat flour. 1.20 1 35-370 c. 4’/2 hrs., then let stand 14 hrs. 2 50 1.19 21/4 hrs., then let stand 14 hrs. On the other hand, since alcohol of 50 per cent. strength 1.23 3 60 Z’/4 hrs., then let stand 14 hrs. by weight extracts as much or more protein than alco4 75 1.45 21/4 hrs.. then let stand 14 hrs. 2’/> hrs., then let stand 14 hrs. hol of any other strength, it would seem perfectly 5 75 1.58 6 25-27 1.18 Shake 1 h r . , usual method logical that j o per cent. by weight alcohol should (Test No. 5 made a t a different time from Test No. 4.) be generally used for the determination of alcoholFrom this table it appears that there is no increase soluble protein in wheat flour. As a result of work reported in this paper the folin the amount of gliadin extracted with rise in temperalowing conclusions seem justified. ture, until a temperature just below t h a t a t which I . For the determination of alcohol-soluble protein the alcohol boils is reached. The two samples extracted a t 75’ C. a t different times gave quite in wheat flour, shaking the sample vigorously and different results. Extracting with hot alcohol is continuously for 60 t o 90 minutes in a machine, or more difficult of operation and does not seem t o offer otherwise, gives equally as high results as when the any advantage over extracting in the cold. Unless ordinary method, covering a period of from 18 t o 24 hours, is followed. 1 Food I m p . and Anal., 1st E d , p. 232 2 . While boiling alcohol extracts slightly more pro2 J Am. Chent. Soc., No. 11 (1906) 10-20
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T H E ] O U R N A L OF I N D U S T R I A L A N D ENGINEERIiVG C H E r l f J S T R Y .
tein than cold alcohol, there does not appear t o be any advantage in its use. 3 . Alcohol varying in strength from 4 j per cent. t o 5 5 per cent. b y weight extracts more protein than alcohol of any other strength, hence it is recommended t h a t j o per cent. b y weight alcohol be used for the determination of gliadin in wheat flour, and that the use of 7 0 per cent. alcohol, whether b y weight or b y volume, be discontinued. DIVISIONO F AGRICULTURAL CHEMISTRY A N D S O I L S , MINNESOTA EXPERIMENT STATION, ST. P A U L .
THE DETECTION OF BENZOIC ACID IN COFFEE EXTRACT. By HERMANc I.YTHGOE A N D CL.4RENCE E Recerved July 21, 1911
MARSH
I n testing a sample of coffee extract for benzoic acid by extracting with ether and testing the ether extract in the usual way with ferric chloride, a precipitate was obtained corresponding to ferric benzoate except in color, but on subliming this precipitate the crystals did not have the characteristic appearance of benzoic acid. A portion of the original sample was then acidified with phosphoric acid and subjected t o distillation with steam. The distillate was made alkaline with sodium carbonate, evaporated t o about 5 0 cc., acidified, extracted with ether, and the ether extract was extracted with ammonia. The ammoniacal solution was then evaporated until free from ammonia and ferric chloride was added which produced a precipitate with the same characteristics as in the previous instance. A sample of coffee extract was then made from pure coffee, and upon repeating these tests this extract was found t o act the same as the commercial extract. A large number of coffee extracts were made from different varieties of coffee and in all cases they reacted in the same manner. The ammonium salt of this substance which was extracted with ether was found t o give precipitates with salts of manganese, nickel, magnesium, calcium, and barium, as well as salts of iron and copper, while benzoates will produce precipitates only with salts of iron and copper, and from these differences the following
Nov.,
1911
method for the detection of benzoic acid in coffee extract has been devised: Make the solution acid and extract several times with ether. Wash the combined ether extracts with water and extract with ammonia. Evaporate the ammoniacal extract to a small volume, adding ammonia from time to time t o prevent it from becoming acid, and add a solution of manganese sulphate. Filter through a small filter, wash with as little water as possible and add ferric chloride t o the.filtrate when a dark greenish precipitate will occur if benzoic acid is present. Evaporate to dryness in the casserole in which the precipitation was made, and sublime b y placing an inverted funnel covered with a filter paper in the dish and heating over an asbestos gauze. Remove the funnel, and determine the melting point of some of the crystals which, if benzoic acid, should be 12I .4 ' C. The rest of the crystals may be dissolved in ammonia, the excess of ammonia evaporated a n d ferric chloride added, when the characteristic fleshcolored precipitate will occur if benzoic acid is present. For quantitative purposes the method of Edmund Clark1 was employed with good results as the natural reacting substance has but little influence. Determinations made on pure extracts b y this method gave from 0.01 t o 0.04 per cent. benzoic acid and a correction can be readily made if desired. The accompanying table gives the analyses of a sample of coffee extract made in the laboratory and of two commercial extracts, one of which contained benzoic acid and glycerine, being very deficient in coffee: ANALYSESOF COFFEE EXTRACTS.
Made in laboratory.. 1 . 0 5 9 1 3 . 5 6 2 . 5 0 0 . 2 2 Commercial. .. . . . . 1,057 13.40 2.29 0.17 Commercial.. . ... . . 1 , 0 7 0 2 1 . 4 2 0 93 0 . 5 8
.
0.36 0.42 0.15
0.67 0.70 0 14
. .. . .. . . 0.19
DEPARTMENT OF FOOD AND DRUGINSPECTION. IvASSACHUSETTS S T A T E BOARDOF HEALTH, BOSTON.
PLANTS AND MACHINERY ment of different gases demonstrating the practicability of the method for commercial purposes. The reasoning on which the operation of the meter Received September 5 , 1911. is based is this: The specific heat of most gases is The application of the electric meter t o commercial measurement of gases first suggested itself t o Pro- a quantity already accurately determined and i t is fessor Carl C. Thomas while carrying on extensive known t h a t this value changes but slightly through experiments on the specific heat of superheated steam wide ranges of temperature and pressure. If a n at Sibley College and the University of Wisconsin. electric heater be placed in a pipe line through which These investigations required the use of some form there is a constant flow of gas, and the heater give of heating device. The difficulty of direct quantitive off heat a t a constant rate, the gas temperature is measurements of heat except b y electrical measuring raised a certain fixed amount. Any change' in gas instruments finally required the adoption of electric flow under these conditions will mean a change in heaters. The great convenience of these heaters its temperature increase, an increase in gas flow in this work led t o a series of tests on the measure*Science, Aug 20, 1909 p 253 THE THOMAS GAS METER. B y H . N. PACKARD.
