elimination of sources of infection of crop dustrial Research has just been issued; it plants.

covers the period from August 1, 1918, to The writer appreciates the danger of gen- July 31, 1919. Earl Curzon, of Kedleston, eralizing upon such a subject. However the the Lord President, records that during the two conditions, the one a prompt utilization

past year the work of the Department of Sciof all vegetable material and the other an entific and Industrial Research has steadily almost entire absence of leaf spot diseases,

grown in usefulness and in amount. The are both so noticeable that the coincidence and

passage from war to peace, he says, reveals suggested explanation seem worthy of note.

more and more clearly as it proceeds the ATHERTON LEE

need for the sympathetic encouragement and BUREAU OF PLANT INDUSTRY

organization of research in every sphere of

national life. Encouraging progress is reA METHOD OF IMBEDDING IN PARAFFINE

corded in several directions. Thus a marked The following method of imbedding tissues

change is observed to be taking place in the in paraffine preparatory to sectioning has

attitude of industry towards scientific reproven so satisfactory in routine work in our

search; both masters and men are beginning laboratory that this brief note of description

to recognize its vital importance. Something is offered.

also has been done to increase the number of The imbedding is done in paraffine buttons formed on the surface of cold water. Melted

trained research workers, the demand for paraffine is allowed to flow from a pipette

whose services rose rapidly not only in indown the side of a glass dish with sloping dustries, but also in the universities and govwall, such as a finger bowl, nearly full of

ernment departments. The report of the Adwater. On reaching the surface, the paraffine visory Council, signed by the administrative hardens below, forming a button still liquid chairman, Sir William McCormick, describes above and anchored securely at one edge to

in greater detail the various branches of the the glass. The tissue is now p'aced in the

department's work. The work of the Food fluid paraffine and oriented. More paraffine Investigation Board grew enormously during may then be added to thicken the button if the year. The field to be covered is so large necessary. A label is attached by its end and the range of scientific knowledge so wide, with a small drop of paraffine. The button is that only a complex organization could hope then disengaged from the class by a dissecting to deal with the problems effectively. The necdle and carried on the point of the latter board accordingly set up six' committees to below the surface. It is at once transformed deal respectively with fish preservation, engito a glass of water inverted over a basin, neering, meat preservation, fruit and vegewhere it remains until solid.

tables, oils and fats, and canned foods; and Large thick buttons may be obtained in this these committees have in turn appointed way without the use of glycerin, paper boats seven special committees. The therapeutic or frames. The rapidity with which imbed- uses of oxygen, shown by recent practise to ding may be done by this method is perhaps be capable of very great extension, and being its chief recommendation.

actively investigated by the Medical Research LEO H. SCHATZ

Committee in close cooperation with the REED COLLEGE

Oxygen Research Committee of the Depart

ment. The Industrial Fatigue Research QUOTATIONS

Board was established jointly by the Medical SCIENTIFIC AND INDUSTRIAL RESEARCH IN Research Committee and the Department, the ENGLAND

former being responsible for administration. The fourth annual report of the Committee The demands made upon the Board have far of the Privy Council for Scientific and In- exceeded all anticipation, while industrial unrest, believed by many to be closely related to itself gives a defective image. Rings of blue present ignorance of the laws of fatigue and or red encircle each bright object, and in the best modes of applying them in practise, place of points of light there appear hazy

, has emphasized the importance of this branch circles or fantastic comet-like shapes. If at of research.—British Medical Journal.

the center of the field a picture is fairly good,

the parts toward the edge are distorted. To SCIENTIFIC BOOKS

improve such crude images, at least two Constructional Data for Small Telescope Ob

lenses must be used in combination. Accordjectives. Calculated at the National Phys

ingly data are here given for suitably

matched two-lens objectives, one lens of ical Laboratory. By T. Smith and R. W.

crown glass, the other of flint glass, so proCHESHIRE. 4to. Pp. 32. Additional data for the construction of small telescopes ob

portioned as to eliminate at least two of the

so-called aberrations, or defects of the image. jectives. By the same authors. Prepared

The figures relate to six kinds of crown glass at the request of the Director General of

(a seventh in the supplement) and six kinds Munitions Supplies. 4to. Pp. 82. London, Harrison and Sons, 1915 and 1916. Price,

of flint glass. The selection of typical sorts 2s. 6d. and 5s.

is not made at random, nor at equal intervals

in the whole range of possibilities, but near During the war every possible stimulus and aid was offered to manufacturers by the Eng

what we may call, borrowing a statistical

term, accumulation points of the catalish government no less liberally than by our

logue list. To suit each of six sets of conown, and of course some years earlier. The present volume is intended to save the manu

ditions the proper dimensions are found for facturer of small telescopes a large part of

every combination of one kind of crown with the time and expense that would be con

one kind of flint, so that every table contains

36 entries. sumed in perfecting his models. British glass factories, aroused to the emergency, had

The first set of tables (A) eliminates color

and spherical aberration; not, of course, for succeeded in producing new varieties and a

all kinds of light and for objects at all large quantity of optical glass, duplicating in feverish haste inventions evolved at leisure

possible distances, but for two different wave by German scientists and artisans during the

lengths of light and for objects at a distance previous thirty years. But the grinding of

so great that the rays striking the glass are lenses and their combination into effective

practically parallel ("object at infinity ").

To the removal of color from the image corresets for binoculars, gun-sights, range-finders and photographic cameras can not be begun

sponds an algebraic equation of the first until protracted mathematical calculations are

degree between the focal lengths of the two finished. Years of preliminary study have

lenses, both considered as "thin"; while that often gone into the making of an improved

for spherical aberration is of the third degree objective. One must conjecture, design, cal- in the curvatures, or reciprocals of the radii culate and compare. Obviously, carefully

of the spherical surfaces of the lenses. But systematized records of previous studies would when the two lenses are to be in contact, and save labor: cooperation is economy. These their contiguous surfaces are exactly alike so tables mark a new application of this prin- that they may be cemented, the third degree ciple. Glass factories supply, with a list of equation for that common radius is reduced available melts, their indices of refraction and by one degree, to a quadratic. For this equadispersion. By the tables one can decide

tion then there are two solutions, and so two quickly upon the comparative merits of tables of curvatures. Indeed all the pairs doublets made from those materials.

here tabulated are cemented lenses. Since Objectives are usually made of from two to two of the four spherical surfaces have equal six separate lenses. Each component by radii for any desired focal length, there re

one

main only two unknowns to be determined So far, it has been assumed that the thickby conditions which will eliminate aberra- ness of the lenses is so small as to be neglitions. For the first, our authors select color gible. Of course the diameter that is needed -chromatic aberration. The second condi- for a particular purpose may cause a thicktion in one case that for spherical aberration; ness which is far from negligible, especially in another, for coma; and in a third case, in types having one or more fairly large curfor equality of three radii instead of merely vatures. To allow for this, the authors fix two. Evidently therefore this publication, arbitrarily a “ standard thickness" of onethough valuable as a first, is only the first fortieth the focal length for a convex lens, among a large number of desirable thesauri one eightieth for a concave, and furnish for for optical designers.

these standards thicknesses tables of two Of two solutions for the same physical sorts. The first shows how much the focal condition, equally correct mathematically, length is diminished by standard thickness

may prove in practise far superior. when one uses the radii taken from a thinTables A and B enable us to compare these lens table, and the second shows by what two, both free from spherical aberration, amount the curvature of the fourth surface thirty-six samples of each. To the cautious (the most nearly flat) may be modified to tyro, and also, it appears, to the expert, it restore the focal length to its intended value, seems better to select surfaces of small curva- unity. ture where possible; although in microscopes, Such an alteration of one surface is howas Abbe demonstrated, such counsel is often ever only a make-shift, as is seen from the misleading. Taking as unit the focal length later tables (1916), “Additional data,” etc. of the combined lenses, Table A shows radii To alter the curvature of a single one of the of curvature varying from 0.2977 to 5,000 or, four surfaces disturbs not only the focal for the cemented surface alone, from 0.2977 length, but also the precise balance of both to 0.4671. The second solution, or Table B, the aberrations which are already eliminated. shows radii for this middle surface of from The authors recommend it indeed only when 0.1705 to 0.3495. On this account therefore the focal length is to be short. Otherwise it Table A gives the more useful patterns. An is necessary to change slightly all three curadditional table gives for each type the vatures from the 1915 tables. Very full inamount of

left uncorrected, which formation is given as to the amount of averages nearly the same for A as for B.

change. First they give factors for interBoth A and B are calculated for the ar- polation when either index differs slightly rangement of crown lens preceding, flint fol- from that for which the earlier tables were lowing. The reversed arrangement is pro- computed. Then back to this table are vided for in Tables E and F, and these call referred, in the next following series, the for radii which are individually and on the effects of standard thickness upon chromaaverage considerably smaller, curvature there- tism. Namely, the corresponding change to fore greater; but in E, the coma remaining be made in the ratios of indices for flint and in the system is somewhat reduced. Other crown is stated, so that by two tables the tables are for forms where three radii are changes of curvatures can be found. Next equal and the fourth surface nearly flat, so comes the effect upon spherical aberration that the cost of grinding might be lessened resulting from standard thickness, and last, even though the telescope would be less effi- the necessary changes in curvatures to correct cient. These last are accompanied by an

that error.

But it is recommended that when exhibit of the residual amount of both two kinds of aberration simultaneously bespherical aberration and coma. Two further come serious in amount, the curvatures be tables promise freedom from coma, with computed entirely de novo, since the errors stated amounts of uncorrected spherical aber- are not wholly independent. Such computaration.

tion is of course greatly facilitated by knowl

coma

or

edge of any approximate values for the radii; cium proteinate, etc.; and (3) protein acids, and this constitutes one of the chief reasons e. g., protein chloride or protein sulfate, etc. for expecting these tables to prove generally For gelatin the hydrogen ion concentration serviceable.

defining the isoelectric point is, as Michaelis The authors deserve the thanks of optical first showed, about 2 x 10-5 N (or in Sörencomputers further, in particular, for their sen's logarithmic symbol pH=4.7). At this care in testing results by trigonometrical cal- hydrogen ion concentration gelatin can pracculations. Judging from more than a hun- tically combine with neither anions nor cations dred such verifications, they inform us, the of an electrolyte. When the hydrogen ion small errors in the approximate values of concentration becomes lower than 2 x 10-5, spherical aberration occur only in the fourth e. g., through the addition of NaOH, part of decimal place, so that they would hardly in- the isoelectric gelatin is transformed into fluence the specifications to be given to the sodium gelatinate, and the relative amount of mechanician. The data in the first tables isoelectric non-ionogenic gelatin transrun to three decimal places.

formed into sodium gelatinate increases with Of major significance are the graphs, pages the diminution of the hydrogen ion concen80 and 81, showing the performance of tration. Sodium gelatinate can exchange its typical lenses of the various types at different cation with the cation of neutral salts but apertures. Group A makes quite the best is not (or practically not) affected by the showing. The final page, with some general anion of a neutral salt. When we raise the conclusions, may well be read first.

hydrogen ion concentration of gelatin soluAmerican readers will have noticed already, tions above that of the isoelectric point, e. g., from certain reports published by the Bureau by adding HCl, isoelectric gelatin will be of Standards, that projects not wholly dis- transformed into gelatin chloride and the similar to this have been under consideration, transformation will become the more comand are already partially realized, for lighten- plete the higher the hydrogen ion concentraing the arduous labor of finding satisfactory tion, until finally all the isoelectric gelatin is first approximations in definite types of lens transformed into gelatin chloride. The geladesign.

HENRY S. WHITE tin-acid salts can exchange their anion with BUREAU OF STANDARDS

the anion of other salts but are not (or prac

tically not) affected by the cation of other SPECIAL ARTICLES

salts.2

While isoelectric gelatin has a minimal ELECTROLYTES AND COLLOIDS

osmotic pressure, a minimal power of swellThe effect of ions on the physical properties ing, a minimal viscosity, a minimal transof proteins is one of the most interesting

parency,

a minimal alcohol number, etc., chapters of colloid chemistry. The work on

gelatin salts, e. 9., sodium gelatinate or this topic quoted in the textbooks of colloid

gelatin chloride, have a high osmotic preschemistry suffers from two sources of error,

sure, a high power of swelling, a high visnamely, first, that the effect of the hydrogen

cosity, etc. The writer has been able to show ion concentration is generally ignored, and

by volumetric analysis that the osmotic pressecond, that the effect of the nature of ions

sure, the power of swelling, etc., of gelatin on the physical properties of proteins is often

increase with the relative amount of isoelecascertained in the presence of an excess of an

tric gelatin transformed into gelatin salt. electrolyte. Proteins are amphoteric electro

The physical properties of gelatin, e. g., its lytes and therefore occur in three states

1 Michaelis, L., “Die Wasserstoffionenkonzentraaccording to the hydrogen ion concentration,

tion,” Berlin, 1914. namely as: (1) protein, free from ionogenic

2 Loeb, J., J. Gen. Physiol., 1918-19, I., 39, 237. impurities, (isoelectric protein); (2) metal 3 Loeb, J., J. Gen. Physiol., 1918-19, I., 237, 363, proteinates, e. g., sodium proteinate or cal

483, 559.

osmotic pressure, depend therefore not only acid, being transformed into gelatin-acid upon the concentration of the gelatin in salts.) solution but also upon the hydrogen ion con- The same difference as between sodium and centration.

calcium gelatinate exists between gelatin Colloid chemists usually state only the chloride and gelatin sulfatet and this differamount of acid added to a protein without ence is also obliterated when neutral salt or measuring the hydrogen ion concentration of acid is added to the solution. (The addition their protein solution. The effect of the of an excess of alkali would transform the addition of the same amount of acid upon gelatin acid into isoelectric gelatin and the chemical and physical properties of finally into metal gelatinate.) gelatin is entirely different according to the If we wish to investigate the specific effect hydrogen ion concentration of the gelatin of different ions on the physical properties used. When a slight amount of acid is of gelatin (or of proteins in general) it is added to isoelectric gelatin it will increase therefore necessary to avoid an

excess of its osmotic pressure while the same amount electrolytes. The writer proceeds in the folof acid if added to gelatin with a pH=3.3 lowing way. Finely granulated (commercial) or to neutral gelatin (pH=7.0) will dimin- gelatin is brought to the isoelectric point by ish its osmotic pressure. Since the hydrogen the method described in the writer's previous ion concentration of commercial gelatin publications. Isoelectric gelatin if properly varies and since, moreover, the combining washed will lose its ionogenic impurities. power of different acids with gelatin varies Just enough acid or alkali is then added to also, the results obtained by the addition of 1 gm. of isoelectric gelatin to produce a electrolytes without measurement of the hy- gelatin salt (either gelatin acid or metal drogen ion concentration are irregular and gelatinate) of the desired hydrogen ion conconfusing.

centration. Since there exists an equilibIn addition, the properties of gelatin salts rium between free acid (or free alkali) depend upon at least two more variables, gelatin salt and isoelectric (non-ionogenic) namely, the nature of the ion in combination gelatin two solutions of metal gelatinate (e. g., with the gelatin and the concentration of

Na gelatinate and Ca gelatinate) each conelectrolyte present. When we transform 1

taining 1 gm. of isoelectric gelatin and each per cent. solutions of isoelectric gelatin into

possessing the same hydrogen ion concentrasodium gelatinate and calcium gelatinate both

tion contain the same proportion of metal possessing the same hydrogen ion concentra

gelatinate and non-ionogenic gelatin. Differtion (e. 9., 10-9) the sodium gelatinate has

ences in the physical properties of these two osmotic pressure more than twice as

solutions may be ascribed to differences in great as the calcium gelatinate. This differ

the effect of the metal ion in combination ence is not due to a difference in the degree with the gelatin. The same is true for soluof electrolytic dissociation since both solu

tions of gelatin chloride and gelatin sulfate tions have the same conductivity.5 When we

of the same hydrogen ion concentration if add increasing quantities of neutral salts or

prepared from isoelectric gelatin of the same alkalies to the two solutions the osmotic

concentration. If this procedure is not folpressure is depressed in both solutions and lowed, erroneous results will be obtained such if enough is added the osmotic pressure falls

are found in the textbooks of colloid to almost zero in both solutions. (If we add

chemistry. Thus it is generally stated that acid, the same will occur but for another

acids and alkalies increase the osmotic reason, the metal gelatinate being brought to

pressure of gelatin while neutral salts depress the isoelectric point, and, by addition of more

it. This statement is entirely wrong and due 4 Loeb, J., J. Gen. Physiol., 1918–19, I., 559.

to the fact that the experimenter responsible 6 Loeb, J., J. Gen. Physiol., 1918-19, I., 483. for this statement did not work with gelatin

an

as