THE PEANUT INDUSTRY. 111. PEANUT PRODUCTS* D. F. J. LYNCH, WASHINGTON, D. C .
Peanut Butter Types of Peanuts Used.-In any consideration of peanut products the manufacture of peanut butter must have a prominent place. This food-product industry is about twenty-five years old. From 1907-19 the industry had its most rapid growth, increasing five-fold within the twelve years. Since 1919, however, there has been little increase in the consumption of peanut butter. The industry accounts for six to eight million bushels of peanuts ann~ally.'~The types used by the peanut butter manufacturers are the Virginia, the Spanish, and the Southeastern Runner. The Valencia peanuts make an excellent quality of peanut butter but the cultivation of this variety is hampered-because of the tendency its pods have of dropping off the vines in the harvesting. The grade of nuts selected by the manufacturer is, however, more important than the variety. No. 3 peanuts, which consist of broken kernels and small shriveled peas, known as "pegs," should never be used for the preparation of peanut butter. A few factories do however use No. 3 peanuts in making butter, sometimes called "confectioners' peanut butter." When received from the cleaners the No. 3 goods are dumped into tubs of water; the sticks and trash are scooped off the top; dirt and stones sink quickly to the bottom; and the peanuts in between are removed and then slightly picked over before being ground into butter.18 Q Method of Manufacture.-Peanut butter is generally prepared by grinding well-roasted and carefully blanched peanuts, and, as a rule, contains no other ingredient, except salt. The quality depends, to a great extent, upon the grade of nuts selected, but to a degree upon the variety of nuts chosen, or more often upon the proportion of the different varieties blended in its preparation, and also upon the care exercised in the following operations. Many manufacturers use a mixture of Virginia and Spanish nuts in the preparation of their product, explaining that the Virginias absorb the excess oil of the Spanish nuts and give a beautifully smooth and fine-flavored butter. Roasting.-The actual production of peanut butter consists, usually, of six steps which are grouped into four operation^.^^ The first step in the process is the roasting. By far the majority of the manufacturers buy shelled goods for roasting, although there are some who roast un*Part I of this series of artides appeared in Tars JOWRNN.,7, 794-811 (Apr., 1930); Part 11, 7, 1037-50 (May, 1930). =Am. Food J., 22, 134 (Apr., 1927). l9 Bur. PIenl Industry Circular 98 (1912), U. S. Dept. of Agriculture. The Spice Mill. 44, 1850 (1920). 1277
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shelled nuts. In such a plant the shelling of the nuts should be carried out in another building, because the dust of a shelling plant is sure to contaminate the butter if both processes are carried on in the same building. The roasting of shelled goods demands considerable care as upon this step depends the flavor and color of the h a 1 product. The source of heat for roasting varies from natural gas to a coke fire. The operation is carred on a t about 320°F. and the time required varies from 20 to 60 minutes. The goal aimed at, in the roasting, is perfect uniformity in the product. This uniformity is attained by slowly rotating the roasting cylinder and accurately regulating the heat. The interior of the roasting cylinder should be smooth and the movement slow, otherwise the red skin loosened by the heat will be rubbed off and the kernel burnt and discolored. The accurate control of a draft of aif through the roasting batch and out of the cylinder aids the operator in obtaining uniformly roasted nuts. The shelled nuts are fed into the roasting cylinder through a large hopper a t the top. This hopper is of sufficient size to hold a full charge of nuts for the roaster and, therefore, little time is lost after the unloading of one batch before the roaster is turning again with its next charge. Cooling.-The step following the roasting is known as cooling. When the batch has reached the desired color i t is discharged from the roasting cylinder into the cooling box. Batches are usually described by the operators as a "high-roast" or a "mild-roast." Some markets prefer the "higher-roasted nuts. The "mild-roast" is considered, by the majority of the people, however, as more palataye and wholesome. Too light roasting, on the other hand, produces a peanut butter lacking in flavor, color, and good keeping qualities. To obtain perfect uniformity and prevent some of the kernels from becoming too brown, artificial cooling is necessary. This is accomplished in the cooling box which is equipped with a false bottom and a connection with a suction lime. Air is drawn down through the hot batch a t such a rate as to effect a reasonable rapid cooling of the nuts. After cooling, the connection with the suction lime is broken and the cooling box, which is on wheel, is rolled to a bucket elevator or floor hopper and there unloaded. The elevator or floor hopper controls the flow of goods for the effectiveoperation of the blanching machine. Blanching.-In the next operation-blanching-the red skin and the 'heart" of the kernel are removed. Both detrimentally affect the palatability of the butter and the skins also affect the appearance. The presence of any considerable quantity of hearts in the peanut butter is also believed to promote premature rancidity. A specky appearance results if the skins are ground with the meats, and they give a slightly bitter taste to the butter.*l The blancher is constructed of corrugated plates U. S. Dept Ag-7. Bull. No. 1401.
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which hold the nuts momentarily while the revolving brushes remove the *skins. A suction or blast line removes the skins to a collecting chamber. These red skins can be sold to the oil pressers as the oil content is high enough to make the commercial extraction of the oil profitable. The operation of blanching is very important and much care is demanded in the design of the blancher to attain the desired well-blanched kernels with the smallest amount of "meal." The machine should be constructed so as to allow adjustment of the brushes while running, and allowance should also be made for easy access to the interior of the machine for complete inspection and keeping clean all parts of the machinery which come in contact with this food product. This operation should be called split-nut blanching to distinguish it from the blanching as carried on by the Virginia salted peanut producer, where the desired product is the whole kernel. In this blancher the kernels are split by the plates and then thrown on a screen which sifts out the "hearts" and broken kernels known as "meal" and carries the half kernels on to the next process. The hearts, the other by-product of blanching, can also be sold as they have gained some popularity as a pigeon and poultry feed. Cleaning and Picking.-The blanched split kernels are then subjected to cleaning and hand picking. Even the best commercial grade of nuts contain some shriveled or unsound kernels. The extent to which the cleaning must be carried a t this point depends on the grade of stock purchased and the quality of the peanut but$er desired. High-quality peanut butter can be prepared from a lower grade of stock if the cleaning and hand picking is such that all the imperfect nuts are removed. No. 2 nuts differ from No. 1 nuts in the size of all the nuts in that class and the number or percentage of shriveled kernels allowed in that grade. Sound No. 2 nuts are just as sound as sound No. 1 nuts, differing only in size. It is, therefore, for the individual manufacturer to decide whether he will buy No. 2 nuts a t a lower price and spend more money on his cleaning and hand-picking operation. The material to be removed from the sound half-kernels is either sufficiently heavier or lighter than the kernels to effect a good air separation. The goods pass through a carefully regulated upward blast of air which lifts the kernels and the lighter material, allowing the undesirable heavier material to fall out into a receptacle below. The efficiencyof this separation is affected by the fact that the kernels are made lighter by roasting and the splitting has given more surface to the lifting air blast. The kernels with the lighter material are then deposited on a moving belt which, in carrying the kernels to the picking tables, bring them under the "chaffer." The "chaffer," by means of a carefully regulated suction, picks out and carries away the loose, light, foreign material.
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PICKING TABLEIN A PEANUT-BUTTER PLANT Burnt peanuts and foreign matter are fernoved by hand and light material by suction before the peanuts pass to $he peanut-butter mill.
Hand picking of the nuts is needed if only to act as an inspection of the goods and as a check on the efficient operation of the plant. After passing under the "chaffer" the moving belt cames the goods smoothly and a t a slow speed over the picking table. The hand pickers sit on both sides of the table and inspect the flow of kernels as they pass, removing the imperfect nuts. The work here increases with a drop in quality of the raw stock purchased and without any drop in efficiency of the preceding operations. In the operations referred to, the manufacturers will lose 5 pounds in 100 pounds of average No. 1shelled nuts in the roasting, an additional 9 pounds in blanching and 1-11/%pounds in the hand-picking o p e r a t i ~ n . ~ ~ Mixing.-If the producer desires a peanut butter made from more than one variety he usually mixes the nuts at this point, just before grinding. As mentioned above the nuts can be mixed in the roasting cylinder but this method makes the blanching and cleaning more dif6cult and less efficient. Today most plants use special mixers of which the "twoconveyor mixer" is an example. Two short screw conveyors, mounted side by side and connected by spur gears, carry the nuts to the grinder. Plant I%dustry Circular 98 (1912).
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The tooth ratio of these gears determine the relative speed and therefore the relative amounts of the two varieties of nuts delivered to the mill. Sets of gears are purchased with these mixers which will vary the proportions of the nuts delivered to the mill as desired. Grinding.-The actual grinding of the kernels is not difficult. The grinding mill desirable in a peanut-butter plant should be variable a t will, for producing a product which may vary from a distinctly grainy consistency to a "dead smooth paste. It should be so constructed that the grinding parts can he easily removed for the replacement of new disks as well as afford convenient access to the interior of the mill for cleaning. It has been learned by experience that the most important requirement in the grinding operation, for the delivery of a uniform butter, is to keep the mass under a constant pressure throughout the mill.. The popular mill, today, is built to meet this need. In the center of the mill is a heavy revolving screw which forces along the crushed mass at a constant pressure through a pair of adjustable grinding disks, into the discharged spout, for delivery in a continuous stream to the peanut-butter containers. I t is upon this constant pressure that the desired uniform consistency of peanut butter depends. There is, of course, attached to the mill an automatic salt feeder. The amount of salt added varies with the manufacturer and the market which he is supplying at the time, but usually amounts to 1 to 4% of the weight of the butter. The best grade of dairy salt is used and it must be uniformly distributed throughout the product. The operator of the grinding mill desires to break apart the minute oil cells but does not wish to injure the cell and liberate the oil. If he succeeds the butter is finely granular. A too coarse grind produces a butter that has an objectionable gritty feel. A smooth pasty consistency, on the other hand, would indicate a liberation of the oil with attending injury to the oil cell. When consumed this "dead smooth butter bas the disagreeable tendency of sticking to the roof of the mouth. Grinding plates which have been worn smooth tend to rub and injure the cell, so as to liberate the oil, giving a paste which lacks the proper cousistency and does not hold up well. A similar inferior butter is also caused by the overheating of the crushed nuts in the grinding mill. Packing.-Although it is the usual custom to fill the peanut-butter containers a t the grinding mill, a few plants are equipped with separate filling machines. When the jars are full they are capped with covers under a high vacuum. There is only one added precaution which the peanut butter manufacturer must observe above those precautions generally necessary in packing any good product. Rubber must not be used in the rings which are customarily put under the cap to effect an air-tight seal. Rubber is somewhat soluble in peanut oil. There is a large amount of peanut butter sold "in bulk," which means in large pails which are not sealed air-
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FILLING GLASSJARS WITH PEANUT BUTTER The peanuts drop into the hopper at the top of the mill, are ground up, nothing but salt is added, and the completed product, peanut butter, comes out the spout.
tight. Exposed to air the butter will not keep as long and soon becomes rancid. Very often proper care is not exercised in the retailing of peanut butter in bulk. The product is allowed to stand uncovered and exposed to dust. No attempt seems to be made to make its appearance inviting and in general there exists much to be desired in the present method of selling this grade of peanut butter.
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F~LING CAPPING, , AND LABELING GLASSJARSOF PEANUTBUTTER An endless belt carries the jars from one machine to another.
Keeping Quality-The distributors and consumers of peanut butter encounter only two difficulties. The first one is the separation of the oil on the top of the butter. The directions to stir up the butter and oil are all right but all prefer a product that does not have to be stirred up. F. W. S t o ~ k t o nadvocates ~~ the addition of hydrogenated peanut oil or other solid fat and grinding the mixture into a homogeneous mass and U. S. Pat. 1,395,934.
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claims that the separation of the oil on the top of the butter is thus prevented. W. W. Wi1lison2' claims to accomplish the same result by incorporating 10 per cent of water in the butter which he claims serves to expand the starch cells so that segregation of the oil is prevented. J. L. Rosenfield suggests that we prepare a product with the desired properties by removing a major portion of the oil in peanut butter and mix with the residue, while hot, some hydrogenated edible oile5and he considers the replacing of a portion of peanut oil with cocoanut oil will impart to the product the desired characteristic. J. H. Beattie and A. M. Jacksone6 claim to have solved this difficulty for the peanut butter manufacturers by subjecting the peanut butter in air-tight containers to steam pressure a t 250 degrees Fahrenheit for fifteen minutes. I t is claimed that this patented treatment prevents the subsequent separation of the oil from the solid material in the peanut butter and also improves the keeping quality of this food product. Samples subjected to this treatment are reported to have been kept in ordinary storage for periods of two years or more without the development of rancidity or the separation of the oil from the solid matter. The other undesirable characteristic of peanut butter is the tendency it has of clinging to the roof of the mouth. Many manufacturers claim that this can be avoided by a change in the mill to produce a coarser product. D. W. Howe claims that this tendency can be prevented in any peanut butter by the uniform distribution throughout the product of about 5 per cent of de~trose.~' Analyses.-R. 0.Baird of North Dakda" has made a large number of analyses of the various brands of peanut butter. He reports as minimum and maximum results that the moisture content varied from 1.21-2.54 per cent and the ash amounted to 2.09-3.4 per cent. He found 1.54-2.31 per cent crude fiber in the butter. The main components-crude fat, protein, and nitrogen-free extract-varied 43.8S55.30 per cent, 29.9334.05 per cent and 7.22-17.82 per cent, respectively. It can be safely assumed that the fat content in peanut butter will be about 45 per cent, the protein content nearly 30 per cent and the carbohydrate content nearly 17 per cent. Jaffa2#gives 2825 calories per pound as the fuel value of this food. The people of this country spend something over $10,000,000 a year on peanut butter, consuming about two-thirds of a pound per capita.30
" U.
S . Pat. 1,398,352, U. S. Pat. Reissue 15,918. "U. S . Pat. No. 1,731,647, Oct. 15, 1929. " U. S . Pat. 1,696,766, Dec. 25, 1928. " N. D. Slate Food Comm. & C h m . Bull., 3, 1 3 (1923). F a r m s Bulletin 332, U. S. Dept. of Agriculture. $0 F. E. Craxton, Am. Food 3.. 22, 134 (April, 1927).
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ROLLING OUT PEANUTCANDY,PREPARATORY TO CUTTING IT UP INTO 5-CSNT BARS The iron "rails" at the sides of the table keep the candy to a uniform thickness.
Peanut Candy
*
As users of shelled peanuts the candy makers are nearly as important as the salters and peanut-butter manufacturers. Although shelled Runners are sometimes substituted for Virginias in the cheaper grades of candy, this demand is supplied chiefly with No. 1 Spanish and Virginia nuts. Extra large grade Virginia nuts are sometimes substituted for almonds in chocolate bars. The peanuts usually reach the consumer of peanut candy in the form of peanut brittle or peanut bars. Peanut brittle is the older form of peanut candy and is still in demand by the public. I t is composed of peanuts and sirup made from cane sugar and glucose. Of recent years, until the present dieting fad became so popular with the consuming public, each week saw a material increase in the demand for the 5-cent candy bar. Large amounts of peanuts are used by the manufacturers of this type of candy. The peanut bar is also composed of peanuts and a sirup of glucose and cane sugar, which is often coated with chocolate. A newer type of peanut confectionery is sugar-coated peanuts which are known to the trade as "burnt peanuts." These are prepared by thinly coating the nuts while warm with a simp. During the operation the kernels are tumbled in a pan and by rubbing against each other
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CUTTING PEANUT CANDYINTO &CENT BARS As the candy hardens quickly, the cuttilig must immediately follow the rolling to a uniform thickness.
*
the kernels acquire the desired roughened appearan~e.~'Of late some of the peanut crop has been absorbed by the bakeries in the production of peanut cookies, peanut jumbles, and, upon grinding, for sprinkling on the top of bakery products. Peanut Flour Another form in which peanuts may reach the consuming public is known as peanut flour. Peanut flour can be obtained directly from raw or roasted peanuts or from peanut cake. Peanut cake is the residue left in the oil press after pressing out the peanut oil. Only that peanut cake made from pressing the best grade of shelled nuts is available for peanut flour. If made by grinding up the whole kernel the flour has, of course, the same composition as the peanut. When made, as usual, from peanut cake the flour is a very high protein foodstuff. Peanut flour is wholesome, palatable, and nutritious, containing four times as much protein, eight times as much fat, and nine times as much mineral ingredients as white wheat flour.32 For bread-making the addition of 81 U. S. Dept. BBu 1401. 32
U. S. Dept. of Agriculture Yearbook, 1917, pp. 295-6.
MAKING "SUGAR-COATED PEANUTS,'' KNOWNAS "BURNTPEANUTS" BY TEE TRADE Note the steam coils around the outside of the revolving pans.
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about two or three parts of peanut flour to ten of white flour is advised by the experts in home economics. Although a considerable amount of peanut flour was used during the war as a wheat substitute, the demand dropped after the war. Nutrition Value of Peanuts and Peanut Products Palatability is the governing factor in the introduction of a new food product, but its sustained consumption over a period of years must depend on its wholesome and nutritious qualities. The digestibility of peanuts has been studied by A. D. Holmes. Mr. Holmesfed steam-cooked soy bean and peanuts and the soy-bean flour and peanut flour in comparative experiments to young men engaged in moderately active pursuits.33 Peanuts or soy beans or their respective flours were the source of protein in a 3100-3240 calorie diet. No digestive or other physiological disturbances were noted. Eighty-six per cent of the peanut flour was digested, which compares favorably with other cereal proteins and is higher than other legume proteins. Since fat-soluble vitamin A and water-soluble vitamin B are present in peanut flour, it seemed to this investigator that peanut flour was especially valuable as a food for men. During the digestion proteins are broken down into about sixteen amino acids which in the body are formed into new proteins. The value of a protein depends on the relative quaptities of the various amino acids it gives on digestion. Some proteins lack entirely those amino acids necessary for growth and will not therefore suJport life. Peanut protein contains all the amino acids necessary for This fact was experimentally demonstrated with white rats. Peanuts are therefore very valuable in supplementing cereals which are deficient in certain of these essential substances. It is not difficultto digest the peanut either in form of peanut flour or peanut butter, but these are concentrated foods, supplying about 2500 calories to the pound, which is sufficient energy for twentyfour hours for the normal person. Lichnikov in his search for the amino acids which make up peanut protein successively extracted the protein with water, 70 per cent alcohol, 10 per cent solution of sodium chloride, and a 0.25 per cent solution of KOH. Upon the hydrolysis of globulin the amino acids histidine, arginine, and lysine were ~ e p a r a t e d . ~ I t~is to C . 0. Johns and his co-workers that weare indebted for most of our knowledge of the proteins in peanuts. In 1916 these chemists isolated from the peanut the two globulins, arachin and ~ o n a r a c b i n . ~Upon ~ analysis of these two proteins arachin yielded 0.4 per >W.S.Dept. of Agriculture Bull. 717; see also J. Am. Med. Assoc., 74, 798 (1920). C. 0. Johns. Cotfan Oil Press,2. No. 12, 41-2. Rec. 6 a u . Lab. Agron.. 9, 378-85 (1913). J. Bid. Chenz.. 28, 77-87 (1916).
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cent sulfur and 4:96 per cent basic nitrogen, while conarachin gave 1.09 per cent sulfur and 6.55 per cent basic nitrogen. In the case of conarachin this is the highest recorded basic nitrogen in any seed protein, and this discovery led these men to suggest peanut flour as a food to supplement cereals and other seeds whose proteins are deficient. In 1917 the same investigators hydrolyzed both of these proteins into their amino acids and made the following report:a7
TABLEI Arginine Histidine Lysine Crystine
Arochin
Conarnchin
13.51% 1.88 4.98 0.85
14.60% 1.83 6.04 r.07
They were also able to obtain a qualitative test for tryptophan. The above content of lysine is high, approaching the lysine content of muscle. I t may be remarked here that wheat and corn are deficient in lysine. In 1918 these same chemists isolated from arachin other rare amino acids in the following amounts: alanine, 4.11 per cent; valine, 1.13 per cent; leucine, 3.88 per cent; proline, 1.31 per cent; phenylalanine, 2.61 per cent; aspartic acid, 5.25 per cent; glutarnic acid, 16.69 per cent; and tyrosine, 5.5 per cent.38 With a food product as important to mankind as the peanut there would be naturally a large amount of nutrition research. Johns and Finks demonstrated that with peanut flour as the 8nly source of protein in an otherwise adequate diet the coefficients of digestibility for peanut protein, fat, and carbohydrate, are respectively, 89 per cent, 96 per cent, and 97 per experi~~ cent. Upon this diet young rats showed normal g r o ~ t h . Feeding ments with rats using peanuts as the source of protein by A. L. Daniels and R. Ponghlin show that this protein, which contains considerable amounts of water-soluble vitamin B, is adequate for normal growth, maintenance, and reproduction.40 In 1928 W. H. Eddy and R. S. Eckman carried out comparative experiments with rats to determine the relative values of meat:and:peanut proteins. The diets were so planned that with the exception of the protein they were otherwise equal. In these experiments peanut flour proved slightly superior to meat in producing growth and markedly superior in the promotion of reproduction." As might be expected marked interest in the nutritive value of peanuts has been manifested in the Orient. T. Shiba and M. Kayama report that J. Bid. Chem., 30, 33-8 (1917). aP
Ibid.. 36.491-500 (1918). ~ r n . ~ o ; J., d 14,NO. 4.2 (1919);see also J. BBi. Chem.,42, 569-79 (1920) J. B i d . Chm.. 33, 29S301 (1918).
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peanut protein is superior to that of the soy bean in producing while N. Suzuki and his co-workers find that peanuts are to be preferred to rice as a source of protein.4a K. L. Mackenzie-Wallis4' finds that quite apart from the oil the nutritive value of peanut flour is high. Not only is the flour an efficient source of protein, but it is rich in amino acids which make it anti-scorbutic and therefore excellent for supplementing the rich carbohydrate diet of the natives of India. The work of E. D. W. Grieg demonstrated that biscuits made from peanuts were equal in antiscorbutic potency to the best brand of atta biscuits previously examined, and therefore this investigator recommends peanut biscuits as emergency rations for troops in India.'"ther experimental work has indicated other possible special food uses for peanut flour. M. B. Church, through her & group fermentation work with molds from the ~ s p e v ~ i l l .flaws-oryzae for the preparation of soy bean sauce, suggests the utilization of peanut cake as suitable for the production of similar sauces.46 Due to the small quantity of utilizable carbohydrate in peanut flour as compared with wheat flour and soy bean flour (which is the common diabetic food), M. K. M. Neale on the other hand suggests a new use for peanut flour in his recommendation that it be substituted for soy-bean flour in diabetic foods.47 From the foregoing scientific work it can readily be seen that peanut products are wholesome and nutritious. They far surpass in these respects many food articles which are consunied in larger quantities by our people. As an economic source of protein, peanut products compare favorably with any we have. The protein found in peanuts have been proved to be rich in the rare but important amino acids. All of us can testify to the palatableness of first-grade peanut foodstuffs. So there exists multiple evidence for the continued increasing use of peanut products in our nation's diet.
.
J. Chem. Soc. Japan, 44, 5 8 4 8 (1923). Sci. Papers Inst. Phys. Chem. Research, 4, 1 4 7 . "Indian J. Med. Res. 6, 45-55 (1918). 45 Ibid., 6, 143-6 (1918). 46 Spice Mill, 47, 168 (1924). 47 J. Am. Dielet. Assoc., 2, 7 3 4 5 (1926). '1
Chemical Centenaries in 1930. Among anniversaries which occur in 1930 are a number of chemical interest. Three hundred years ago was born Kunckel (16301703). a German chemist. The year 1830 was a "vintage year," for in it were barn the Frenchman Raault (1830-1901) whose work helped to lay the foundationsof physical chemistry, and who received the Davy Medal of the Royal Society in 1892; the Dutchman van Bemmelen (1830-1911), also a physical chemist; and the German Lothar Meyer who made contributions to our knowledge of the periodic classification of the elements, especially by his famous curve of the atomic volumes.-Chem. Age
