QD UNIVERSITY OF CALIFORNIA PUBLICATIONS IN PHYSIOLOGY Vol. 5, No. 4, pp. 23-69 March 29, 1919 TABLE OF PH, H+ AND OH~ VALUES CORRE- SPONDING TO ELECTROMOTIVE FORCES DETERMINED IN HYDROGEN ELECTRODE MEASUREMENTS, WITH A BIBLIOGRAPHY. ! CARL L. A.j SCHMIDT AND D. R. HOAGLAND UNIVERSITY OF CALIFORNIA PRESS BERKELEY UNIVEESITY OF CALIFOENIA PUBLICATIONS Note. The University of California Publications are offered in exchange for the publi- cations of learned societies and institutions, universities and libraries. Complete lists of all the publications of the University will be sent upon request. For sample copies, lists of publications and other information, address the Manager of the University Press, Berkeley, California, U. S. A. All matter sent in exchange should be addressed to The Exchange Department, University Library, Berkeley, Calif crnia, U. S. A. PHYSIOLOGY. S. S. Maxwell, Editor. Price per volume $2. Volumes I (pp. 217), II (pp. 215), III ^3. 197), and IV (pp. 228) completed. Volume V in progress. '...* Voi/S/ J." JCJie/ Control of Heliotropic Eeactions in Fresh-water Crustaceans by Chemicals, especially CO 3 (a preliminary communication), by ;:*;*.". ^ .3acqijes Loeb. Pp. 1-S. November, 1904. .05 *T .**!. *1 ta^vftffcHsr Experiments on Heterogeneous Hybridization in Eehinoderma, by Jacques Loeb, Pp. 5-30. December, 1904 8. Influence of Calcium and Barium on the Secretory Activity of tha Kidneys (second communication), by John Bruce MacCallum, Pp. 31-42. December, 1904. 4. Note on the Gaivanotropie Eeactions of the Medusa Polyorchis penicillata A, Agassiz, by Frank W. Bancroft. Pp. 43-46, Decem- ber, 1904. Nos. 2, S and 4 in one cover .48 5. The Action on the Intestines of Solutions containing two Salts, by John Bruce MacCallum. Pp. 47-64. January, 1905. 6. The Action of Purgatives in a Crustacean (Sida crystalline'), by John Bruce MacCallum. Pp. 65-70. January, 1905. Nos. 5 and 6 in one cover .26 7. On the Validity of Pfluger's Law for the Galvanic Action of Para- mecium (preliminary communication), by Frank W. Bancroft. P. 71. February, 1905. 8. "On Fertilization, Artificial Parthenogenesis and Cytolysis of the Sea urchin Egg, by Jacques Loeb. Pp. 73-81. February, 1905. Nos. 7 and 8 in one cover 15 9. On an Improved Method of Artificial Parthenogenesis, by Jacques Loeb. Pp. 83-86. February, 1905... .05 10. On the Diuretic Action of Certain Haemolytics, and the Action of Calcium in Suppressing Haemoglobinuria (preliminary communica- tion), by John Bruce MacCallum. Pp. 87-88. March, 1905. 11. On an Improved Method of Artificial -Parthenogenesis (second com- munication), by Jacques Loeb. Pp. 89-92. March, 1905. Nos. 10 and 11 in one cover .^- 05 12. The Diuretic Action of Certain Haemolytics and the Influence of Calcium and Magnesium in Suppressing the Haemolysis (second communication), by John Bruce MacCallum, Pp. 93-103. May, 1905. 18. The Action of Pilocarpine and Atropin on the Flew of Urina, by John Bruce MacCallura. Pp. 105 112. May, 1905. Nos. 12 and 13 in one cover .28 14. On an Improved Method of Artificial Parthenogenesis (third com- munication), by Jacques Loeb. Pp. 113-128. May, 1905 _ .18 15. On the Influence of Temperature upon Cardiac Contractions and its Eolation to Influence of Temperature upon Chemical Eeaction Velocity, by Charles D, Snyder. Pp. 125-146. September. 1905 26 16. Artificial Membrane Formation and Chemical Fertilization in a Star- fish (Astet-ina)., by Jacques Loeb, Pp. 147-158. September, 1905 15 17. On the Influence of Electrolytes upon the Toxicity of Alkaloids (pre- liminary communication), by T. Brailsford Eobertson. Pp. 159-162. October, 1905 _~ - .05 18. Studies on the Toxicity of Sea-water for Fresh- water Animal* (Gammarus pulex De Geer), by C. H. Wolfgang Ostwald. Pp. 163-191; plates 1-6. November, 1905 85 19. On the Validity of Pfltiger's Law for the Galvanotropic Eeactions of Paranieciuia, by Frank W. Bancroft. Pp. 193-215; 8 text figures. November, 1905 20 Vol.8, 1. On Chemical Methods by which the Eggs of & Mollusc (Lottia Gigantea) can ba caused to become Mature, by Jacques Loeb. Pp. 1-8. November, 1905 05 2. On the Changes In the Nerve and Muscle which ssem to Underlie the Electrotonic Effect of the Galvanic Current, by Jacques Loeb. Pp. 9-15. December, 1905 ~ 05 UNIVERSITY OF CALIFORNIA PUBLICATIONS IN PHYSIOLOGY Vol. 5, No. 4, pp. 23-69 March 29, 1919 TABLE OF PH, H+ AND OH" VALUES CORRE- SPONDING TO ELECTROMOTIVE FORCES DETERMINED IN HYDROGEN ELECTRODE MEASUREMENTS, WITH A BIBLIOGRAPHY.* BY GAEL L. A. SCHMIDT AND D. E. HOAGLAND (From the Hearst Laboratory of Pathology and Bacteriology, the Department of Biochemistry, and the Division of Agricultural Chemistry of the University of California.) The importance of measurements of reaction or hydrogen ion concentration is well recognized in many fields of scientific work. In biological studies the reaction of the body tissues and fluids, optimum reaction for enzymes, and the dissociation of the proteins are among the many subjects investigated. Recent work has shown the impor- tance of the reaction of the media for the proper growth of micro- organisms, and in the field of agricultural chemistry the relation of the acidity of the soil to the growth of the plant has also been indi- cated. The extensive application of the electrometric method for determining hydrogen ion concentration has led to its use in labora- tories without extensive equipment, and where the extreme accuracy so necessary to the theoretical chemist is less essential than the ability quickly to carry out a large number of determinations without the use of refined apparatus. The results so obtained may still have an accuracy well within the limits of interpretation. With a view of facilitating measurements of hydrogen ion concen- tration, one of us (Schmidt) 37 some years ago prepared tables for the conversion of voltages into hydrogen or hydroxyl ion concentrations, thus rendering unnecessary the somewhat tedious computations. Since * Aided in part by a grant from the George Williams Hooper Foundation for Medical Eesearch. 821905 "24 University of California Publications in Physiology [VOL. 5 then Sorensen's suggestion of using P H * as a measure of reaction instead of hydrogen ion concentration has been quite generally adopted and the expression of results simplified. For many purposes, however, . both units are desirable. McClendon 172 has published a chart from "*.>* . '.wllifefi; both of the above values within a certain range can be read. *: ;";"'/Th;e coujtinited demand for, as well as the advantages possessed by a direct 'conversion table led us to recalculate the former tables and include also the P H values for both the normal and N/10 KCl-calomel electrode. For a range of voltages not frequently used the calculations have been made, as in the former tables, for every two millivolts, while for a certain range on either side of the neutral point this has been done for each millivolt. We have also included an extensive bibliography, somewhat arbi- trarily classified, since it is quite impossible to arrange the references according to the subjects treated without either duplicate citation or cross-indexing. While many of the references given possess merely historical interest, they have nevertheless been included and are of value as showing to what extent certain fields have been investigated. We have cited only those references which include determinations of hydrogen ion concentration by the electrometrie method, by indicators, or by the use of buffer mixtures. Certain other references appertain- ing to the theory of the hydrogen electrode or methods of measuring electromotive forces have also been included. Our calculations are based on the recent measurements by Lewis, Brighton, and Sebastian 61 of the potential of the normal and N/10 KCl- calomel electrodes and the dissociation constant of water. For the potential of the normal calomel electrode, referred to the potential of the normal hydrogen electrode as zero, we have taken H 2 ,H+ (M) || Hg, HgCl, KC1 (M) ; E = 0.283 volt * The term PH is given to the exponent of 10 taken as a positive number. This is the most rational system since all values are expressed in the same units. Thus CH = 5.03 X 10" 10 can be expressed entirely as a power of 10. 5.03 = 10- 702 (since Iog 10 5.03 = 0.702) CH = 10- 702 X 10- 10 _ 3 Q-9.298 PH 9.298 Another example : To find PH, when CH = 0.409 X 10' 7 PH = log 10 05 PH = Iog 10 1 Iog 10 CH Log 10 CH = 10- 7 X lO 1 - = 8.612 PH = 17.388 10 PH = 7.388 Schmidt-Hoagland: Table of P H , H+ and OH- Values 25 and for the difference in potential between the normal and N/10 KC1- calomel electrodes Hg, HgCl, KC1 (0.1 M) || HgCl, KC1, (M) ; E = 0.053. This gives a value of 0.336 volt for the N/10 KCl-calomel electrode, a millivolt less than the value (0.337 volt) which most biological investi- gators have assigned to this electrode. However, if the latter value is adopted the table can still be used ; it is merely necessary to shift the values given under the column E N one millivolt. For the dissociation 10 constant of water we have taken Kw = 1.012 X 10- 14 (25C) which gives a concentration of H + and OH" as VKw= 1.006 X 10- 7 . The value of Kw is stated by Lewis, Brighton, and Sebastian 61 to be correct within two or three per cent. All calculations in the table have been made on the temperature basis of 25 C. This value has been most generally used for physico-chemical work and is well within the range of room temperature in laboratories having no special facili- ties for temperature regulation. For small temperature variations this error, as will be shown later, is usually negligible. For the calcuation of hydrogen ion concentration (C H ) the well- known Nernst equation RT , 1 * In nF "(C H ) is used, where E, r=:gas constant in volt coulombs (8.31574). T = absolute temperature (273.09 + 25). n = valency of hydrogen (1). F = Faraday constant (96,500 coulombs). In = natural logarithm. In - = log M TT = difference of potential between the E.M.F. measured and the potential of the particular calomel cell used. C H = concentration of hydrogen ion to be determined. At 25 C we have ,r = 0.059152 Iog 10 -^ = 0.059152 P H . _ CH * To be more exact, according to recent physico-chemical views it is the activity of the H-ion rather than the concentration which is measured. Numerically, however, the value is the same. 26 University of California Publications in Physiology [VOL. 5 This equation gives at once both the values for P H and CH- To illus- trate : when the voltage, using the N/10 KCl-calomel electrode, is 0.773 0.773 0.336 = 0.059152 P H 0.059152 Iog 10 ^~ P H = 7.388 H = Iog 10 C H 1 C H = antilog. JL H C H = 10.000 10 -7.388 2.612 10 or 7 X 1.612 CH = 0.409 X 10- 7 1.012 X IP" 4 _o 47vl o-T 0.409 X10- 7 The values calculated for C H and P H have been carried to three decimals and those for C O H to two decimals. These are accurate to one unit in the last decimal place. For most purposes, however, it is sufficiently accurate to express values one decimal place less than given in the table. The results given in the tables are based on a hydrogen pressure of 760 millimeters. It requires a considerable divergence from this pressure to produce a change in voltage within the accuracy of the tables. Loomis and Acree 65 have investigated the influence of pressure on the hydrogen electrode and found that a change of forty milli- meters in the barometric pressure produced a change in the potential of only 0.0007 volt. It is evident that the ordinary barometric fluctua- tions are of no significance except in physico-chemical researches. If necessary, however, to correct for partial hydrogen pressures, it may be done as follows: E b = E.M.F. measured at the barometric pressure b. e b = E b 0.336 (for the N/ KCl-calomel electrode) . 0.05915 . 760 e 760 = e b - log ~^- E 760 = e 760 + 0.336. The correction will be positive when b is less, and negative when greater than 760 millimeters. Temperature has a somewhat greater influence on the potential of the hydrogen electrode, and varies with the range of C H + measured. Since our tables have been calculated on the temperature basis of 1919] Schmidt-Hoagland: Table of P H , H + and OH- Values 27 25 C, it will be necessary, if measurements are made at any other temperature, to convert the measured voltage to the value it would have at 25 C. Within ordinary temperature ranges the value for the calomel cell on the basis of P H will not change, hence it is merely necessary to correct e t . E t = voltage measured at the temperature t. e t =E t 0.336 (when the N/10 KCl-calomel electrode is used). e 25 = e t X Factor. E, 5 = voltage at 25 C. E 25 = e 25 + 0.336. pm From the Nernst equation it will be seen that the value for will nF change with the temperature, since T is the variable. "We have calcu- lated a series of factors for use within ordinary temperature ranges for the conversion of e t to the value e 25 . Temperature Factor (Multiply) 18 1.024 19 1.021 20 1.017 21 1.014 22 1.010 23 1.007 24 1.004 25 1.000 26 0.996 27 0.993 28 0.990 29 0.987 30 0.983 At the neutral point the change in voltage per degree of temperature variation will be about two millivolts, for P H = 4 this will be only one millivolt, and for P H = 11 it will rise to about three millivolts. The large variety of apparatus used by different authors gives the investigator considerable choice for the particular purpose intended. For many biological, bacteriological, and agricultural investigations measurements accurate to two millivolts are within the limits of interpretation. For this purpose the method outlined by Hildebrand 27 and used extensively by Sharp and Hoagland, 365 ' 37 in which the voltage is directly measured by a voltmeter, is well adapted. The direct-reading potentiometer of Bovie 2 is useful for certain types of work. Where greater accuracy is required, such as the standardiza- 28 University of California Publications in Physiology [VOL. 5 tion of buffer mixtures, reaction changes occurring in the digestion of proteins by enzymes and the dissociation of proteins, the use of a potentiometer with a sensitive galvanometer is essential. The potentiometer manufactured by Leeds and Northrup is very con- venient for this purpose. Rapidity combined with accuracy is obtained by shaking the solution in contact with the hydrogen gas and electrode. For many purposes equilibrium may be quickly obtained by shaking the vessel by hand; more convenient, however, are the motor-driven shakers. For this purpose the electrode vessel designed by Clark 3 and used extensively by Clark and Lubs 111 is most convenient. Hydrogen is best generated electrolytically. Electrolysis of a 25 per cent KOH solution using nickel electrodes, or a 6 per cent H 2 S0 4 solution using platinum electrodes and elimination of oxygen or ozone by passing the hydrogen over heated platinized asbestos, gives a very pure product. Compressed hydrogen from cylinders adequately purified may also be used. We have always used the Cottrell gauze electrode 118 since it is easily made and gives a large surface. Others have pre- ferred an electrode made of a small sheet of platinum. This is coated with platinum black by deposition in a solution of H 2 PtCl 6 containing a trace of lead acetate. Lewis, Brighton, and Sebastian 01 prefer an electrode of gold coated with iridium. For biological work it is essential that the electrode be saturated with hydrogen before immers- ing in the solution to be tested. The best methods of evaluating the contact potential occurring at the junction of two liquids would be either by direct determination or by calculation, but since for most work neither of these methods can at present be used, it is necessary to reduce the contact potential to a minimum by interposing a saturated solution of KC1 between the solution to be tested and the calomel electrode. For this purpose we use glass U tubes filled by placing in a heated solution of 2 per cent washed agar saturated with KCL On cooling the agar solidifies and the KC1 in part crystallizes. A fresh boundary, obtained by cutting small portions off the ends of the glass tube, should be used for each determination. Sand tubes, string dipped in a saturated KC1 solution or a beaker containing the saturated KC1 solution, into which an arm of the electrode vessel dips, diffusion being prevented by using ungreased stopcocks, have also been used. In measuring such systems as soil suspensions, certain protein solutions, etc., contamination from the KC1 should be avoided by the use of a side arm or by leaving 1919] Schmidt-Hoagland: Table of P H , H + and OH- Values 29 the agar tube in contact with the solution for a minimum time, other- wise interreactions may produce changes in the H + concentration. For most work the magnitude of the contact potential when a satu- rated solution of KC1 is interposed is so small that it can be neglected. For very accurate work the extrapolation method of Bjerrum 88 gives the closest approximation. Potential measurements of systems in which C0 2 is a determining factor in the reaction should be carried out in closed vessels, equi- librium being obtained by shaking. The methods used for determining the reaction of blood and body fluids are well adapted for this pur- pose. In soil extracts and nutrient solutions for plants an increase of alkalinity may result from the catalytic reduction of the N0 3 ion by the hydrogen gas. In solutions of high buffer value this effect does not result in any appreciable change in H-ion concentration, but in some solutions a serious error may be caused. It has been noted that thick coatings of platinum black have a much greater catalytic power than thin coatings ; suitable precautions should be taken there- fore when measuring solutions containing nitrates. A reduction of nitrates will be apparent in the gradual increase of voltage during the determination. Under these circumstances a constant value cannot be obtained. There is very little choice between the normal and the N/10 KC1- calomel electrodes, since both are easily reproducible and remain constant. The saturated KCl-calomel electrode is less constant and has a greater temperature variation than either of the other calomel electrodes. Pure materials are necessary. For this purpose the methods described by Loomis and Acree 63 and Hildebrand 103 are well adapted. The glass vessels for the calomel electrode are designed to prevent contamination of the electrode solution and to provide a method for washing out the side arm with KC1 solution. A convenient apparatus is described by Schmidt. 272 For many purposes the use of indicators is a convenience. Many of the indicators used by Friedenthal, 398 Salm, 415 and others have largely been supplanted by indicators of the sulfonphthalein series, 404 ' 405 which offer more convenient ranges of color change. These have been extensively described by Clark and Lubs. 337 For some work it is necessary to test the applicability of a particular indicator by determination of the reaction by the electrometric method. The use of buffer mixtures for the production of solutions contain- ing definite concentrations of hydrogen ions has found extensive 30 University of California Publications in Physiology [VOL. 5 application. A good method whereby the accuracy of a hydrogen electrode system may be tested consists in the determination of the acidity or alkalinity of a carefully prepared buffer mixture. The range of an indicator may likewise be tested this way. Buffer mixtures are usually solutions of acetates, bicarbonates, borates, phosphates, phthalates, or cacodylates. These have been carefully standardized and described in the work of Sorensen, 38 Palitzsch, 113 Clark 111 and others. Schmidt-Hoagland: Table of P H? H + X 10- 13 OH- 0.343 0.396 1.014 0.968 1.05 0.345 0.398 1.048 0.895 1.13 0.347 0.400 1.082 0.828 1.22 0.349 0.402 1.116 0.766 1.32 0.351 0.404 1.150 0.709 1.43 0.353 0.406 1.183 0.656 1,54 0.355 0.408 1.217 0.607 1.67 0.357 0.410 1.251 0.561 1.80 0.359 0.412 1.285 0.519 1.95 0.361 0.414 1.319 0.480 2.11 0.363 0.416 1.352 0.444 2.28 0.365 0.418 1.386 0.411 2.46 0.367 0.420 1.420 0.380 2.66 32 University of California Publications in Physiology [VOL. 5 Ex EN PH CH+ COH- 1 Io X 10- 1 H> X 10- 13 OH- 0.369 0.422 1.454 0.352 2.88 0.371 0.424 1.488 0.325 3.11 0.373 0.426 1.521 0.301 3.36 0.375 0.428 1.555 0.278 3.64 0.377 0.430 1.589 0.258 3.92 0.379 0.432 1.623 0.238 4.25 0.381 0.434 1.657 0.221 4.58 0.383 0.436 1.691 0.204 4.96 0.385 0.438 1.724 0.189 5.35 0.387 0.440 1.758 0.175 5.78 0.389 0.442 1.792 0.162 6.25 0.391 0.444 1.826 0.149 6.79 0.393 0.446 1.860 0.138 7.33 0.395 0.448 1.893 0.128 7.91 0.397 0.450 1.927 0.118 8.58 0.399 0.452 1.961 0.109 9.28 0.401 0.454 1.995 0.101 10.00 EN EN PH CH+ COH- i 10 X 10- 2 H + X 10- 12 OH- 0.403 0.456 2.029 0.936 1.08 0.405 0.458 2.062 0.866 1.17 0.407 0.460 2.096 0.801 1.26 0.409 0.462 2.130 0.741 1.37 0.411 0.464 2.164 0.686 1.48 0.413 0.466 2.198 0.634 1.60 0.415 0.468 2.232 0.587 1.72 0.417 0.470 2.265 0.543 1.86 0.419 0.472 2.299 0.502 2.02 0.421 0.474 2.333 0.465 2.18 0.423 0.476 2.367 0.430 2.35 0.425 0.478 2.401 0.398 2.54 0.427 0.480 2.434 0.368 2.75 0.429 0.482 2.468 0.340 2.98 0.431 0.484 2.502 0.315 3.21 0.433 0.486 2.536 0.291 3.48 0.435 0.488 2.570 0.269 3.76 0.437 0.490 2.603 0.249 4.06 0.439 0.492 2.637 0.231 4.38 0.441 0.494 2.671 0.213 4.75 0.443 0.496 2.705 0.197 5.14 0.445 0.498 2.739 0.183 5.53 0.447 0.500 2.772 0.169 5.99 0.449 0.502 2.806 0.156 6.49 0.451 0.504 2.840 0.145 6.98 0.453 0.506 2.874 0.134 7.55 0.455 0.508 2.908 0.124 8.16- 0.457 0.510 2.942 0.114 8.88 0.459 0.512 2.975 0.106 9.55 Schmidt-Hoagland: Table of P H , H + and OH- Values 33 EN EN PH CH+ COH- 1 To X 10-" B> X 10- 11 OH- 0.461 0.514 3.009 0.979 1.03 0.463 0.516 3.043 0.906 1.12 0.465 0.518 3.077 0.838 1.21 0.467 0.520 3.111 0.775 1.31 0.469 0.522 3.144 0.717 1.41 0.471 0.524 3.178 0.663 1.53 0.473 0.526 3.212 0.614 1.65 0.475 0.528 3.246 0.568 1.78 0.477 0.530 3.280 0.525 1.93 0.479 0.532 3.313 0.486 2.08 0.481 0.534 3.347 0.450 2.25 0.483 0.536 3.381 0.416 2.43 0.485 0.538 3.415 0.385 2.63 0.487 0.540 3.449 0.356 2.84 0.489 0.542 3.483 0.329 3.08 0.491 0.544 3.516 0.305 3.32 0.493 0.546 3.550 0.282 3.59 0.495 0.548 3.584 0.261 3.88 0.497 0.550 3.618 0.241 4.20 0.499 0.552 3.652 0.223 4.54 0.501 0.554 3.685 0.206 4.91 0.503 0.556 3.719 0.191 5.30 0.505 0.558 3.753 0.177 5.72 0.507 0.560 3.787 0.163 6.21 0.509 0.562 3.821 0.151 6.70 0.511 0.564 3.854 0.140 7.23 0.513 0.566 3.888 0.129 7.85 0.515 0.568 3.922 0.120 8.43 0.517 0.570 3.956 0.111 9.12 0.519 0.572 3.990 0.102 9.92 EN EN PH CH+ COH- ~T To X 10- 4 B> X 10- 10 OH 0.521 0.574 4.023 0.947 1.07 0.522 0.575 4.040 0.911 1.11 0.523 0.576 4.057 0.876 1.16 0.524 0.577 4.074 0.843 1.20 0.525 0.578 4.091 0.811 1.25 0.526 0.579 4.108 0.780 1.30 0.527 0.580 4.125 0.750 1.35 0.528 0.581 4.142 0.721 1.40 0.529 0.582 4.159 0.694 1.46 0.530 0.583 4.176 0.667 1.52 0.531 0.584 4.193 0.642 1.58 0.532 0.585 4.210 0.617 1.64 0.533 0.586 4.226 0.594 1.70 0.534 0.587 4.243 0.571 1.77 0.535 0.588 4.260 0.549 1.84 0.536 0.589 4.277 0.528 1.92 0.537 0.590 4.294 0.508 1.99 0.538 0.591 4.311 0.489 2.07 34 University of California Publications in Physiology [VOL. 5 EN EN PH CH+ COH- 1 10 X 10-" H> X 10- 10 OH- 0.539 0.592 4.328 0.470 2.15 0.540 0.593 4.345 0.452 2.24 0.541 0.594 4.362 0.435 2.33 0.542 0.595 4.379 0.418 2.42 0.543 0.596 4.395 0.402 2.52 0.544 0.597 4.412 0.387 2.61 0.545 0.598 4.429 0.372 2.72 0.546 0.599 4.446 0.358 2.83 0.547 0.600 4.463 0.344 2.94 0.548 0.601 4.480 0.331 3.06 0.549 0.602 4.497 0.319 3.17 0.550 0.603 4.514 0.306 3.31 0.551 0.604 4.531 0.295 3.43 0.552 0.605 4.548 0.283 3.58 0.553 0.606 4.564 . 0.273 3.71 0.554 0.607 4.581 0.262 3.86 0.555 0.608 4.598 0.252 4.02 0.556 0.609 4.'615 0.243 4.16 0.557 0.610 4.632 0.233 4.34 0.558 0.611 4.649 0.224 4.52 0.559 0.612 4.666 0.216 4.69 0.560 0.613 4.683 0.208 4.87 0.561 0.614 4.700 0.200 5.06 0.562 0.615 4.717 0.192 5.27 0.563 0.616 4.734 0.185 5.47 0.564 0.617 4.750 0.178 5.69 0.565 0.618 4.767 0.171 5.92 0.566 0.619 4.784 0.164 6.17 0.567 0.620 4.801 0.158 6.41 0.568 0.621 4.818 0.152 6.66 0.569 0.622 4.835 0.146 6.93 0.570 0.623 4.852 0.141 7.18 0.571 0.624 4.869 0.135 7.50 0.572 0.625 4.886 0.130 7.78 0.573 0.626 4.903 0.125 8.10 0.574 0.627 4.920 0.120 8.43 0.575 0.628 4.936 0.116 8.72 0.576 0.629 4.953 0.111 9.12 0.577 0.630 4.970 0.107 9.46 0.578 0.631 4.987 0.103 9.83 EN EN PH CH+ COH- 1 To X 10- 5 H + X 10- 9 OH- 0.579 0.632 5.004 o'.991 1.02 0.580 0.633 5.021 0.953 1.06 0.581 0.634 5.038 0.916 1.10 0.582 0.635 5.055 0.881 1.15 0.583 0.636 5.072 0.848 1.19 0.584 0.637 5.089 0.815 1.24 0.585 0.638 5.106 0.784 1.29 0.586 0.639 5.122 0.754 1.34 Schmidt-Hoagland: Table of P H , H + wnd OH- Values 35 EN Ex PH CH+ COH- i To X 10- 5 H> X 10-" OH- 0.587 0.640 5.139 0.725 1.40 0.588 0.641 5.156 0.698 1.45 0.589 0.642 5.173 0.671 1.51 0.590 0.643 5.190 0.646 1.57 0.591 0.644 5.207 0.621 1.63 0.592 0.645 5.224 0.597 1.70 0.593 0.646 5.241 0.574 1.76 0.594 0.647 5.258 0.552 1.83 0.595 0.648 5.275 0.531 1.91 0.596 0.649 5.292 0.511 1.98 0.597 0.650 5.308 0.492 2.06 0.598 0.651 5.325 0.473 2.14 0.599 0.652 5.342 0.455 2.22 0.600 0.653 5.359 0.437 2.32 0.601 0.654 5.376 0.421 2.40 0.602 0.655 5.393 0.405 2.50 0.603 0.656 5.410 0.390 2.59 0.604' 0.657 5.427 0.374 2.71 0.605 0.658 5.444 0.360 2.81 0.606 0.659 5.461 0.346 2.92 0.607 0.660 5.478 0.333 3.04 0.608 0.661 5.495 0.320 3.16 0.609 0.662 5.511 0.308 3.29 0.610 0.663 5.528 0.296 3.42 0.611 0.664 5.545 0.285 3.55 0.612 0.665 5.562 0.274 3.69 0.613 0.666 5.579 0.264 3.83 0.614 0.667 5.596 0.254 3.98 0.615 0.668 5.613 0.244 4.15 0.616 0.669 5.630 0.235 4.31 0.617 0.670 5.647 0.226 4.48 0.618 0.671 5.664 0.217 4.66 0.619 0.672 5.681 0.209 4.84 0.620 0.673 5.697 0.201 5.03 0.621 0.674 5.714 0.193 5.24 0.622 0.675 5.731 0.186 5.44 0.623 0.676 5.748 0.179 5.65 0.624 0.677 5.765 0.172 5.88 0.625 0.678 5.782 0.165 6.13 0.626 0.679 5.799 0.159 6.36 0.627 0.680 5.816 0.153 6.61 0.628 0.681 5.833 0.147 6.88 0.629 0.682 5.850 0.141 7.18 0.630 0.683 5.866 0.136 7.44 0.631 0.684 5.883 0.131 7.73 0.632 0.685 5.900 0.126 8.03 0.633 0.686 5.917 0.121 8.36 0.634 0.687 5.934 0.116 8.72 0.635 0.688 5.951 0.112 9.04 0.636 0.689 5.968 0.108 9.37 0.637 0.690 5.985 0.104 9.73 36 University of California Publications in Physiology [VOL. 5 EN EN PH CH+ COH- T 10 X 10- 6 B> X 10- 8 OH 0.638 0.691 6.002 0.996 1.02 0.639 0.692 6.019 0.958 1.06 0.640 0.693 6.036 0.921 1.10 0.641 0.694 6.052 0.886 1.14 0.642 0.695 6.069 0.852 1.19 Oi643 0.696 6.086 0.820 1.23 0.644 0.697 6.103 0.789 1.28 0.645 0.698 6.120 0.758 1.34 0.646 0.699 6.137 0.729 1.39 0.647 0.700 6.154 0.702 1.44 0.648 0.701 6.171 0.675 1.50 0.649 0.702 6.188 0.649 1.56 0.650 0.703 6.204 0.625 1.62 0.651 0.704 6.221 0.601 1.68 0.652 0.705 6.238 0.578 1.75 0.653 0.706 6.255 0.556 1.82 0.654 0.707 6.272 0.535 1.89 0.655 0.708 6.289 0.514 1.97 0.656 0.709 6.306 0.495 2.04 0.657 0.710 6.323 0.476 2.13 0.658 0.711 6.340 0.458 2.21 0.659 0.712 6.357 0.440 2.30 0.660 0.713 6.373 0.423 2.39 0.661 0.714 6.390 0.407 2.49 0.662 0.715 6.407 0.392 2.58 0.663 0.716 6.424 0.377 2.68 0.664 0.717 6.441 0.362 2.80 0.665 0.718 6.458 0.348 2.91 0.666 0.719 6.475 0.335 3.02 0.667 0.720 6.492 0.322 3.14 0.668 0.721 6.509 0.310 3.26 0.669 0.722 6.526 0.298 3.40 0.670 0.723 6.543 0.287 3.53 0.671 0.724 6.559 0.276 3.67 0.672 . 0.725 6.576 0.265 3.82 0.673 0.726 6.593 0.255 3.97 0.674 0.727 6.610 0.245 4.13 0.675 0.728 6.627 0.236 4.29 0.676 0.729 6.644 0.227 4.46 0.677 0.730 6.661 0.218 4.64 0.678 0.731 6.678 0.210 4.82 0.679 0.732 6.695 0.202 5.01 0.680 0.733 6.712 0.194 5.22 0.681 0.734 6.728 0.187 5.41 0.682 0.735 6.745 0.180 5.62 0.683 0.736 6.762 0.173 5.85 0.684 0.737 6.779 0.166 6.10 0.685 0.738 6.796 0.160 6.32 0.686 0.739 6.813 0.154 6.57 0.687 0.740 6.830 0.148 6.84 Schmidt-Hoagland: Table of P H , H + and OR- Values 37 EN EN PH CH+ COH- ~1 10 X 10- 8 H + X 10- 8 OH 0.688 0.741 6.847 0.142 7.13 0.689 0.742 6.864 0.137 7.39 ' 0.690 0.743 6.881 0.132 7.67 0.691 0.744 6.898 0.127 7.97 0.692 0.745 6.914 0.122 8.30 0.693 0.746 6.931 0.117 8.65 0.694 0.747 6.948 0.113 8.96 0.695 0.748 6.965 0.108 9.37 0.696 0.749 6.982 0.104 9.73 *0.697 0.750 6.999 0.100 10.12 EN EN PH CH+ COH- 1 10 X 10- 7 H + X 10- T OH 0.698 0.751 7.016 0.964 1.05 0.699 0.752 7.033 0.927 1.09 0.700 0.753 7.050 0.892 1.13 0.701 0.754 7.067 0.858 1.18 0.702 0.755 7.084 0.825 1.23 0.703 0.756 7.100 0.794 1.27 0.704 0.757 7.117 0.763 1.33 0.705 0.758 7.134 0.734 1.38 0.706 0.759 7.151 0.706 1.43 0.707 0.760 7.168 0.679 1.49 0.708 0.761 7.185 0.653 1.55 0.709 0.762 7.202 0.628 1.61 0.710 0.763 7.219 0.604 1.68 0.711 0.764 7.236 0.581 1.74 0.712 0.765 7.253 0.559 1.81 0.713 0.766 7.269 0.538 1.88 0.714 0.767 7.286 0.517 1.96 0.715 0.768 7.303 0.497 2.04 0.716 0.769 7.320 0.478 2.12 0.717 0.770 7.337 0.460 2.20 0.718 0.771 7.354 0.443 2.28 0.719 0.772 7.371 0.426 2.38 0.720 0.773 7.388 0.409 2.47 0.721 0.774 7.405 0.394 2.57 0.722 0.775 7.422 0.379 2.67 0.723 0.776 7.439 0.364 2.78 0.724 0.777 7.455 0.350 2.89 0.725 0.778 7.472 0.337 3.00 0.726 0.779 7.489 0.324 3.12 0.727 0.780 7.506 0.312 3.24 0.728 0.781 7.523 0.300 3.37 0.729 0.782 7.540 0.288 3.51 0.730 0.783 7.557 0.277 3.65 0.731 0.784 7.574 0.267 3.79 0.732 0.785 7.591 0.257 3.94 0.733 0.786 7.608 0.247 4.10 * Neutral point. 38 University of California Publications in Physiology [VOL. 5 EN EN PH CH+ COH- 1 10 X 10- 7 B> X 10- 7 OH 0.734 0.787 7.624 0.238 4.25 0.735 0.788 7.641 0.228 4.44 0.736 0.789 7.658 0.220 4.60 0.737 0.790 7.675 0.211 4.80 0.738 0.791 7.692 0.203 4.99 0.739 0.792 7.709 0.195 5.19 0.740 0.793 7.726 0.188 5.38 0.741 0.794 7.743 0.181 5.59 0.742 0.795 7.760 0.174 5.82 0.743 0.796 7.777 0.167 6.06 0.744 0.797 7.794 0.161 6.29 0.745 0.798 7.810 0.155 6.53 0.746 0.799 7.827 0.149 6.79 0.747 0.800 7.844 0.143 7.08 0.748 0.801 7.861 0.138 7.33 0.749 0.802 7.878 0.132 7.67 0.750 0.803 7.895 0.127 7.97 0.751 0.804 7.912 0.123 8.23 0.752 0.805 7.929 0.118 8.58 0.753 0.806 7.946 0.113 8.96 0.754 0.807 7.963 0.109 9.28 0.755 0.808 7.980 0.105 9.64 0.756 0.809 7.996 0.101 10.02 E N EN PH CH+ COH- i 10 X 10- 8 H> X 10-" OH 0.757 0.810 8.013 0.970 1.04 0.758 0.811 8.030 0.933 1.08 0.759 0.812 8.047 0.897 1.13 0.760 0.813 8.064 0.863 1.17 0.761 0.814 8.081 0.830 1.22 0.762 0.815 8.098 0.798 1.27 0.763 0.816 8.115 0.768 1.32 0.764 0.817 8.132 0.739 1.37 0.765 0.818 8.149 0.710 1.43 0.766 0.819 8.165 0.683 1.48 0.767 0.820 8.182 0.657 1.54 0.768 0.821 8.199 0.632 1.60 0.769 0.822 8.216 0.608 1.66 0.770 0.823 8.233 0.585 1.73 0.771 0.824 8.250 0.562 1.80 0.772 0.825 8.267 0.541 1.87 0.773 0.826 8.284 0.520 1.95 0.774 0.827 8.301 0.500 2.02 0.775 0.828 8.318 0.481 2.10 0.776 0.829 8.335 0.463 2.19 0.777 0.830 8.351 0.445 2.27 0.778 0.831 8.368 0.428 2.36 0.779 0.832 8.385 0.412 2.46 Schmidt-Hoagland: Table of P H , H + and OH- Values 39 EN EN PH CH+ COH- 1 10 X 10- 8 H> X 10- 6 OH- 0.780 0.833 8.402 0.396 2.56 0.781 0.834 8.419 0.381 2.66 0.782 0.835 8.436 0.367 2.76 0.783 0.836 8.453 0.353 2.87 0.784 0.837 8.470 0.339 2.99 0.785 0.838 8.487 0.326 3.10 0.786 0.839 8.504 0.314 3.22 0.787 0.840 8.521 0.302 3.35 0.788 0.841 8.537 0.290 3.49 0.789 0.842 8.554 0.279 3.63 0.790 0.843 8.571 0.269 3.76 0.791 0.844 8.588 0.258 3.92 0.792 0.845 8.605 0.248 4.08 0.793 0.846 8.622 0.239 4.23 0.794 0.847 8.639 0.230 4.40 0.795 0.848 8.656 0.221 4.58 0.796 0.849 8.673 0.213 4.75 0.797 0.850 8.690 0.204 4.96 0.798 0.851 8.706 0.197 5.14 0.799 0.852 8.723 0.189 5.35 0.800 0.853 8.740 0.182 5.56 0.801 0.854 8.757 0.175 5.78 0.802 0.855 8.774 0.168 6.02 0.803 0.856 8.791 0.162 6.25 0.804 0.857 8.808 0.156 6.49 0.805 0.858 8.825 0.150 6.75 0.806 0.859 8.842 0.144 7.03 0.807 0.860 8.859 0.139 7.28 0.808 0.861 8.876 0.133 7.61 0.809 0.862 8.892 0.128 7.91 0.810 0.863 8.909 0.123 8.23 0.811 0.864 8.926 0.119 8.50 0.812 0.865 8.943 0.114 8.88 0.813 0.866 8.960 0.110 9.20 0.814 0.867 8.977 0.106 9.55 0.815 0.868 8.994 0.101 10.00 EN EN PH CH+ COH- i To X 10-" H + X 10- B OH 0.816 0.869 9.011 0.975 1.04 0.817 0.870 9.028 0.938 1.08 0.818 0.871 9.045 0.902 1.12 0.819 0.872 9.062 0.868 1.17 0.820 0.873 9.078 0.835 1.21 0.821 0.874 9.095 0.803 1.26 0.822 0.875 9.112 0.772 1.31 0.823 0.876 9.129 0.743 1.36 0.824 0.877 9.146 0.714 1.42 0.825 0.878 9.163 0.687 1.47 40 University of California Publications m Physiology [ VoL - 5 EN EN PH CH+ COH- i 10 X 10-" H> X 10- 5 OH- 0.826 0.879 9.180 0.661 1.53 0.827 0.880 9.197 0.636 1.59 0.828 0.881 9.214 0.611 1.66 0.829 0.882 9.231 0.588 1.72 0.830 0.883 9.248 0.566 1.79 0.831 0.884 9.264 0.544 1.86 0.832 0.885 9.281 0.523 1.93 0.833 0.886 9.298 0.503 2.01 0.834 0.887 9.315 0.484 2.09 0.835 0.888 9.332 0.466 2.17 0.836 0.889 9.349 0.448 2.26 0.837 0.890 9.366 0.431 2.35 0.838 0.891 9.383 0.414 2.44 0.839 0.892 9.400 0.398 2.54 0.840 0.893 9.417 0.383 2.64 0.841 0.894 9.434 0.369 2.74 0.842 0.895 9.450 0.354 2.86 0.843 0.896 9.467 0.341 2.97 0.844 0.897 9.484 0.328 3.09 0.845 0.898 9.501 0.315 3.21 0.846 0.899 9.518 0.304 3.33 0.847 0.900 9.535 0.292 3.47 0.848 0.901 9.552 0.281 3.60 0.849 0.902 9.569 0.270 3.75 0.850 0.903 9.585 0.260 3.89 0.851 0.904 9.602 0.250 4.05 0.852 0.905 9.619 0.240 4.22 0.853 0.906 9.636 0.231 4.38 0.854 0.907 9.653 0.222 4.56 0.855 0.908 9.670 0.214 4.73 0.856 0.909 9.687 0.206 4.91 0.857 0.910 9.704 0.198 5.11 0.858 0.911 9.721 0.190 5.33 0.859 0.912 9.738 0.183 5.53 0.860 0.913 9.755 0.176 5.75 0.861 0.914 9.772 0.169 5.99 0.862 0.915 9.788 0.163 6.21 0.863 0.916 9.805 0.157 6.45 0.364 0.917 9.822 0.151 6.70 0.865 0.918 9.839 0.145 6.98 0.866 0.919 9.856 0.139 7.28 0.867 0.920 9.873 0.134 7.55 0.868 0.921 9.890 0.129 7.84 0.869 0.922 9.907 0.124 8.16 0.870 0.923 9.924 0.119 8.50 0.871 0.924 9.941 0.115 8.80 0.872 0.925 9.958 0.110 9.20 0.873 0.926 9.974 0.106 9.55 0.874 0.927 9.991 0.102 9.92 Schmidt-Hoagland: Table of P H , H + and OHr Fate 41 EN E N PH CH+ COH- 1 10 X 10- 10 H> X 10- 4 OH- 0.875 0.928 10.008 0.981 1.03 0.877 0.930 10.042 0.908 1.11 0.879 0.932 10.076 0.840 1.20 0.881 0.934 10.110 0.777 1.30 0.883 0.936 10.143 0.719 1.41 0.885 0.938 10.177 0.665 1.52 0.887 0.940 10.211 0.615 1.65 0.889 0.942 10.245 0.569 1.78 0.891 0.944 10.279 0.526 1.92 0.893 0.946 10.313 0.487 2.08 0.895 0.948 10.346 0.451 2.24 0.897 0.950 10.380 0.417 2.43 0.899 0.952 10.414 0.386 2.62 0.901 0.954 10.448 0.357 2.83 0.903 0.956 10.481 0.330 3.07 0.905 0.958 10.515 0.305 3.32 0.907 0.960 10.549 0.282 3.59 0.909 0.962 10.583 0.261 3.88 0.911 0.964 10.617 0.242 4.18 0.913 0.966 10.651 0.224 4.52 0.915 0.968 10.684 0.207 4.89 0.917 0.970 10.718 0.191 5.30 0.919 0.972 10.752 0.177 5.72 0.921 0.974 10.786 0.164 6.17 0.923 0.976 10.820 0.152 6.66 0.925 0.978 10.853 0.140 7.23 0.927 0.980 10.887 0.130 7.78 0.929 0.982 10.921 0.120 8.43 0.931 0.984 10.955 0.111 9.12 0.933 0.986 10.989 0.103 9.83 EN EN PH CH+ COH- i 10 X 10- 11 H> X 10- 3 OH- 0.935 0.988 11.022 0.950 1.07 0.937 0.990 11.056 0.879 1.15 0.939 0.992 11.090 0.813 1.24 0.941 0.994 11.124 0.752 1.35 0.943 0.996 11.158 0.696 1.45 0.945 0.998 11.191 0.644 1.57 0.947 1.000 11.225 0.595 1.70 0.949 1.002 11.259 0.551 1.84 0.951 1.004 11.293 0.509 1.99 0.953 1.006 11.327 0.471 2.15 0.955 1.008 11.361 0.436 2.32 0.957 1.010 11.394 0.403 2.51 0.959 1.012 11.428 0.373 2.71 0.961 1.014 11.462 0.345 2.93 0.963 1.016 11.496 0.319 3.17 0.965 1.018 11.530 0.295 3.43 42 University of California Publications in Physiology [VOL. 5 EN EN PH CH+ COH- i 10 X 10- 11 H + X 10- 3 OH 0.967 1.020 11.563 0.273 3.71 0.969 1.022 11.597 0.253 4.00 0.971 1.024 11.631 0.234 4.32 0.973 1.026 11.665 0.216 4.69 0.975 1.028 11.699 0.200 5.06 0.977 1.030 11.732 0.185 5.47 0.979 1.032 11.766 0.171 5.92 0.981 1.034 11.800 0.159 6.36 0.983 1.036 11.834 0.147 6.88 0.985 1.038 11.868 0.136 7.44 0.987 1.040 11.901 0.126 8.03 0.989 1.042 11.935 0.116 8.72 0.991 1.044 11.969 0.107 9.46 EN EN PH CH+ COH- 1 10 X 10-" H + X 10- 2 OH- 0.993 1.046 12.003 0.993 1.02 0.995 1.048 12.037 0.919 1.10 0.997 1.050 12.071 0.850 1.19 0.999 1.052 12.104 0.786 1.29 1.001 1.054 12.138 0.728 1.39 1.003 ,1.056 12.172 0.673 1.50 1.005 1.058 12.206 0.623 1.62 1.007 1.060 12.240 0.576 1.76 1.009 1.062 12.273 0.533 1.90 1.011 1.064 12.307 0.493 2.05 1.013 1.066 12.341 0.456 2.22 1.015 1.068 12.375 0.422 2.40 1.017 1.070 12.409 0.390 2.59 1.019 1.072 12.443 0.361 2.80 1.021 1.074 12.476 0.334 3.03 1.023 1.076 12.510 0.309 3.28 1.025 1.078 12.544 0.286 3.54 1.027 1.080 12.578 0.264 3.83 1.029 1.082 12.612 0.245 4.13 1.031 1.084 ' 12.645 0.226 4.48 1.033 1.086 12.679 0.209 4.84 1.035 1.088 12.713 0.194 5.22 1.037 1.090 12.747 0.179 5.65 1.039 1.092 12.781 0.166 6.10 1.041 1.094 12.814 0.153 6.61 1.043 1.096 12.848 0.142 7.13 1.045 1.098 12.882 0.131 7.73 1.047 1.100 12.916 0.121 8.36 1.049 1.102 12.950 0.112 9.04 1.051 1.104 12.983 0.104 9.73 Schmidt-Hoagland: Table of P H , H + and OHr Values 43 EN EN PH CH+ COH- 1 10 X 10~ 13 H + X 10- 1 OH 1.053 1.106 13.017 0.961 1.05 1.055 1.108 13.051 0.889 1.14 1.057 1.110 13.085 0.822 1.23 1.059 1.112 13.119 0.761 1.33 1.061 1.114 13.153 0.704 1.44 1.063 1.116 13.186 0.651 1.55 1.065 1.118 13.220 0.602 1.68 1.067 1.120 13.254 0.557 1.82 1.069 1.122 13.288 0.516 1.96 1.071 1.124 13.322 0.477 2.12 1.073 1.126 13.355 0.441 2.29 1.075 1.128 13.389 0.408 2.48 1.077 1.130 13.423 0.378 2.68 1.079 1.132 13.457 0.349 2.90 1.081 1.134 13.491 0.323 3.13 1.083 1.136 13.524 0.299 3.38 1.085 1.138 13.558 0.277 3.65 1.087 1.140 13.592 0.256 3.95 1.089 1.142 13.626 0.237 4.27 1.091 1.144 13.660 0.219 4.62 1.093 1.146 13.693 0.203 4.99 1.095 1.148 13.727 0.187 5.41 1.097 1.150 13.761 0.173 5.85 1.099 1.152 13.795 0.160 6.32 1.101 1.154 13.829 0.148 6.84 1.103 1.156 13.863 0.137 7.39- 1.105 1.158 13.896 0.127 7.97 1.107 1.160 13.930 0.117 8.65 1.109 1.162 13.964 0.109 9.28 1.111 1.164 13.998 0.101 10.02 X 10- 14 H + X NOH- 1.113 1.166 14.032 0.930 1.09 44 University of California Publications in Physiology [VOL. 5 LITERATURE I. GENERAL AND THEORETICAL. A. APPAEATUS. 1 Barendrecht, H. P., A simple hydrogen electrode, Biochem. Jour., 1915, vol. 9, pp. 66-70. 2 Bovie, W. T., A direct reading potentiometer for measuring and recording both the actual and the total reaction of solutions, Jour. Med. Ees., 1915, vol. 33, pp. 295-322. s Clark,- W. M., A hydrogen electrode vessel, Jour. Biol. Chem., 1915, vol. 23, pp. 475-486. * Liebermann, L. v., Platinelektroden zur Bestimmung der H- und OH- lonenkonzentration, Chem. Ztg., 1911, vol. 35, p. 972. s Long, J. H., A simple cell for the determination of hydrogen ion concentration, Jour. Am. Chem. Soc., 1916, vol. 38, pp. 936-939. s McClendon, J. F., New hydrogen electrodes and rapid methods of determining hydrogen ion concentrations, Am. Jour. Physiol., 1915, vol. 38, pp. 180-185. 7 McClendon, J. F., A direct reading potentiometer for measuring hydrogen ion concentrations, Am. Jour. Physiol., 1915, vol. 38, pp. 186-190. 8 McClendon, J. F., and Magoon, C. A., An improved Hasselbalch hydrogen electrode and a combined tonometer and hydrogen electrode, together with rapid methods of determining the buffer value of blood, Jour. Biol. Chem., 1916, vol. 25, pp. 669-681. 9 Walpole, G. S., Gas-electrode for general use, Biochem. Jour., 1913, vol. 7, pp. 410-428. 10 Walpole, G. S., An improved hydrogen electrode, Biochem. Jour., 1914, vol. 8, pp. 131-133. 11 Wilke, E., Ueber eine neue Wasserstoffelektrode und ihre Ver- wendbarkeit, Zeitschr. f. Electrochem., 1913, vol. 19, pp. 857-858. B. GENERAL METHODS. 12 Baragiola, W. I., Concentration of hydrogen ions, Schweiz. Apoth. Ztg., 1914, vol. 52, pp. 641-643, quoted from Chemical Abstr., 1915, vol. 9, p. 349. is Bjerrum, N., Die Theorie der alkalimetrischen und azidi- metrischen Titrierungen, Sammlung chem. u. chem.-tech. Vortrage, 1914, vol. 21, pp. 1-128. i* Bottger, W., Die Anwendung des Elektrometers als Indikator beim Titrieren von Sauren und Basen, Zeitschr. phys. 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F., Shedlov, A., and Thomson, W., Tables for finding the alkaline reserve of blood serum, in health and in acidosis, from the total CO 2 or the alveolar CO 2 or the PH at known CO 2 ten- sion, Jour. Biol. Chem., 1917, vol. 31, pp. 519-525. 32 Michaelis, L., Die Wasserstoffionenkonzentration. Ihre Bedeut- ung fur die Biologic und die Methoden ihrer Messung., 210 pp., Berlin, J. Springer, 1914. ssMuller, P. T., et Allemandet, H., Sur une Electrode a alcali, Jour. Chim. Phys., 1907, vol. 5, pp. 532-556. s^Noyes, A. A., Eeport of the Committee on standard methods for determining small hydrogen-ion concentrations, 8th Intern. Cong. Appl. Chem., 1912, vol. 25, pp. 95-96. 46 University of California Publications in Physiology [VOL. 5 ss Osterhout, W. J. V., and Haas, A. E. C., A simple method of measuring photosynthesis, Science, n.s., 1918, vol. 47, pp. 420-422. 36 Ringer, W. E., The rapid measurement of the hydrogen ion con- centration of liquids, Chem. 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Vor- trage, 1914, vol. 21, pp. 129-174. 289 Hagglund, E, Ueber die garungshemmende Wirkung der Wasserstoffionen, Biochem. Zeitschr., 1915, vol. 69, pp. 181-191. 290 Leberle, H., and Liiers, H., Acid determination in beer by electrometrical methods, Zeitschr. ges. Brau., vol. 37, pp. 177-184, quoted from Chemical Abst., 1914, vol. 8, p. 2447. 291 Liiers, H., Change of hydrogen ion concentration during fer- mentation, Zeitschr. ges. Brau., vol. 37, pp. 79-82, quoted from Chem- ical Abst., 1914, vol. 8, p. 1845. 292 Michaelis, L., Zur Theorie der elektrolytischen Dissoziation der Fermente, Biochem. Zeitschr., 1914, vol. 60, pp. 91-96. 293 Michaels, L., and Davidsohn, H., Die isoelektrische Konstante des Pepsins, Biochem. Zeitschr., 1910, vol. 28, pp. 1-6. 29* Miehaelis, L., and Davidsohn, H., Trypsin und Pankreasnucleo- proteid, Biochem. Zeitschr., 1910, vol. 30, pp. 481-504. 60 University of California Publications in Physiology [VOL. 5 295 Michaelis, L., and Davidsohn, H., Die Wirkung der Wasserstoff- ionen auf das Invertin, Biochem. Zeitsehr., 1911, vol. 35, pp. 386-412. 296 Michaelis, L., and Davidsohn, H., Die Abhangigkeit der Tryp- simvirkung von der Wasserstoffionenkonzentration, Biochem. Zeitsehr., 1911, vol. 36, pp. 280-290. 297 Michaelis, L., and Mendelssohn, A., Die Wirkungsbedingungen des Pepsins, Biochem. Zeitsehr., 1914, vol. 65, pp. 1-15. 298 Michaelis, L., and Menten, M. L., Die Kinetik der Invertin- wirkung, Biochem. Zeitsehr., 1913, vol. 49, pp. 333-369. 299 Michaelis, L., and Pechstein, H., Untersuchungen iiber die Katalase der Leber, Biochem. Zeitsehr., 1913, vol. 53, pp. 320-355. soo Michaelis, L., and Pechstein, H., Die Wirkungsbedingungen der Speicheldiastase, Biochem. Zeitsehr., 1914, vol. 59, pp. 77-99. soi Michaelis, L., and Eona, P., Ueber die Umlagerung der Glucose bei alkalischer Eeaktion; ein Beitrag zur Theorie der Kata- lyse, Biochem. Zeitsehr., 1912, vol. 47, pp. 447-461. 302 Michaelis, L., and Eona, P., Die Wirkungsbedingungen der Maltase aus Bierhefe I. Biochem. Zeitsehr., 1913, vol. 57, pp. 70-83. sos Morse, M., Hydrogen ion concentration in autolysis, Jour. Biol. Chem., 1916, vol. 24, Proc. Soc. Biol. Chem., p. xxvii. 304 Norris, E. V., The hydrolysis of glycogen by diastatic enzymes. Comparison of preparations of glycogen from different sources, Biochem. Jour., 1913, vol. 7, pp. 26-42. sos Palitzseh, S., and Walbum, L. E., Sur la concentration optimale des ions hydrogene pour la premiere phase de la decomposition trypsique de la gelatine (Liquefaction de la gelatine), C.-E. Lab., Carlsberg, 1912, vol. 9, pp. 200-236. soe Palitzseh, S., and Walbum, L. E., Ueber die optimale Wasser- stoffionenkonzentration bei der tryptischen Gelatineverfliissigung, Biochem. Zeitsehr., 1912, vol. 47, pp. 1-35. SOT Eeed, G. B., The relation of oxidase reactions to changes in hydrogen ion concentration, Jour. Biol. Chem., 1916, vol. 27, pp. 299-302. sos Eeed, G. B., Measurement of oxidation potential, and its sig- nificance in the study of oxidases, Bot. Gaz., 1917, vol. 61, pp. 523- 527. 309 Einger, W. E., and Van Tright, H., Einfluss der Eeaktion auf die Ptyalinwirkung, Zeitsehr. f. physiol. Chem., 1912, vol. 82, pp. 484-501. 310 Eobertson, T. B., and Schmidt, C. L. A., On the part played by the alkali in the hydrolysis of proteins by trypsin, Jour. Biol. Chem., 1908, vol. 5, pp. 31-48. 311 Eohonyi, H., Die Veranderung der Wasserstoffionenkonzentra- tion der Pepsinwirkung und das Saurebindungsvermogen einiger hydrolytischer Spaltungsprodukte des Eiweisses, Biochem. Zeitsehr., 1912, vol. 44, pp. 165-179. 312 Eona, P., Zur Kenntnis der Esterspaltung im Blute, Biochem. Zeitsehr., 1911, vol. 33, pp. 413-422. sis Eona, P., and Arnheim, F., Beitrag zur Kenntnis des Erepsins, Biochem. Zeitsehr., 1913, vol. 57, pp. 84-94. si* Eona, P., and Bien, Z., Zur Kenntnis der Esterase des Blutes, Biochem. Zeitsehr., 1914, vol. 59, pp. 100-112. Schmidt-Hoagland: Table of P H , H + and OH~ Values 61 sis Rona, P., and Bien, Z., Vergleichende Untersuchungen iiber Pankreaslipase und Blutesterase, Biochem. Zeitschr., 1914, vol. 64, pp. 13-29. sis Rona, P., and Michaelis, L., Ueber Ester- und Fettspaltung im Blute und ini Serum, Biochem. Zeitschr., 1911, vol. 31, pp. 345-354. SIT Rona, P., and Michaelis, L., Die Wirkungsbedingungen der Maltase aus Bierhefe. II, Die Wirkung der Maltase auf a Methyl- glucosid und die Affinitatsgrbsse des Ferments, Biochem. Zeitschr., 1913, vol. 58, pp. 148-157. sis Rona, P., and Wilenko, G. G., Beitrage zur Frage der Glykolyse IV, Biochem. Zeitschr., 1914, vol. 62, pp. 1-10. 319 Sorensen, S. P. L., Enzymstudien. II, Ueber die Messung und die Bedeutung der Wasserstoffionenkonzentration bei enzymatischen Prozessen, Biochem. Zeitschr., 1909, vol. 21, pp. 131-304. 320 Sorensen, S. P. L., Erganzung zu der Abhandlung: Enzym- studien. II, Ueber die Messung und die Bedeutung der Wasserstoff- ionenkonzentration bei enzymatischen Prozessen, Biochem. Zeitschr., 1909, vol. 22, pp. 352-356. 321 Sorensen, S. P. L., Etudes enzymatiques. II, Sur la mesure et 1 'importance de la concentration des ions hydrogene dans les reactions enzymatiques. C.-R. Lab., Carlsberg, 1909, vol. 8, pp. 1-168, 396-401. 322 Van Slyke, D. D., and Zacharias, G., The effect of hydrogen ion concentration and of inhibiting substances on urease, Jour. Biol. Chem., 1914, vol. 19, pp. 181-210. G. SEA WATER. 323 Haas, A. R. C., The effect of the addition of alkali to sea water upon the hydrogen ion concentration, Jour. Biol. Chem., 1916, vol. 26, pp. 515-517. 324 Henderson, L. J., and Cohn, E. J., Equilibrium between acids and bases in sea water, Proc. Nat. Acad. Sci., 1916, vol. 2, pp. 618- 622. 325 McClendon, J. F., New buffer mixtures, standard tubes, and colorimeter for determining the hydrogen ion concentration of sea water, Jour. Biol. Chem., 1916, vol. 28, Proc. Soc. Biol. Chem., pp. xxx-xxxi. 326 Palitzsch, S., Ueber die Messung und die Grb'sse der Wasser- stoffionenkonzentration des Meerwassers, Biochem. Zeitschr., 1911, vol. 37, pp. 116-130. 327 Palitzsch, S., Sur le mesurage, et la grandeur de la concentra- tion en ions hydrogene de 1'eau salee, C.-R. Lab., Carlsberg, 1911, vol. 10, pp. 85-98. 328 Sorensen, S. P. L., and Palitzsch, S., Sur "1'erreur de sel" dans la mesure colorime'trique de la concentration des ions hydrogene de 1'eau de mer, C.-R. Lab., Carlsberg, 1911, vol. 10, pp. 252-258. 329 Sorensen, S. P. L., and Palitzsch, S., Sur le mesurage de la concentration en ions hydrogene de 1'eau de mer, C.-R. Lab., Carls- berg, 1910, vol. 9, pp. 8-37. 330 Sorensen, S. P. L., and Palitzsch, S., Ueber die Messung der Wasserstoffionenkonzentration des Meerswassers, Biochem. Zeitschr., 1910, vol. 24, pp. 387-415. 62 University of California Piiblioations in Physiology [VOL. 5 III. BACTERIOLOGICAL. 331 Ayers, S. H., Hydrogen-ion concentrations in cultures of streptococci, Jour. Bact., 1916, vol. 1, pp. 84-85. 332 Beniasch, M., Die Saureagglutination der Bakterien, Zeitschr. f. Immunitatsfrsch. u. exper. Therap., 1912, vol. 12, pp. 268-315. 333 Clark, W. M., The influence of hydrogen-ion concentrations upon the physiological activities of Bacillus coli, Science, n.s., 1915, vol. 41, p. 624. * 33* Clark, W. M., The final hydrogen ion concentrations of cultures of Bacillus coli, Jour. Biol. Chem., 1915, vol. 22, pp. 87-98. 335 Clark, W. M., The "reaction" of bacteriologic culture media, Jour. Infec. Dis., 1915, vol. 17, pp. 109-136. sse Clark, W. M., and Lubs, H. A., The differentiation of bacteria of the colon-aerogenes family by the use of indicators, Jour. Infec. Dis., 1915, vol. 17, pp. 160-173. 3 37 Clark, W. M., and Lubs, H. A., The colorimetric determination of hydrogen ion concentration and its applications in bacteriology, Jour. Bact., 1917, vol. 2, pp. 1-34, 109-136, 191-236. 338 Gillespie, L. J., The acid agglutination of pneumococci, Jour. Exper. Med., 1914, vol. 19, pp. 28-37. 339 Grote, L. E., Ueber die praktische Verwertbarkeit der Saure- agglutination nach Michaelis, Centrbl. Bakt. Orig., 1913, vol. 69, pp. 98-104. 340 Heimann, W., Die "Saureagglutination" innerhalb der Typhus- Paratyphusgruppe, insbesondere sogenannter Paratyphus- C- Baccillen, Zeitschr. f. Immunitatsfrsch., 1912, vol. 16, pp. 127-140. 341 Henderson, L. J., and Webster, H. B., The preservation of neutrality in culture media with the aid of phosphates, Jour. Med. Ees., 1907, vol. 16, pp. 1-5. 342 Homer, A., The reaction of sera as a factor in the successful concentration of antitoxic sera by the methods at present in use, Biochem. Jour., 1917, vol. 11, pp. 21-39. 343 Hurwitz, S. H., Meyer, K. F., and Ostenberg, Z., On a colori- metric method of adjusting bacteriological culture media to any optimum hydrogen ion concentration, Proe. Soc. Exper. Biol. and Med., 1915, vol. 13, pp. 24-26. 344 Hurwitz, S. H., Meyer, K. F., and Ostenberg, Z., A colorimetric method for the determination of the hydrogen ion concentration of biological fluids, with special reference to the adjustment of bacterio- logical culture media, Johns Hopkins Hosp. Bull., 1916, 27, pp. 16-24. 345 Itano, A., The relation of hydrogen ion concentration of media to the proteolytic activity of Bacillus subtilis, Mass. Agr. Exp. Sta. 1916, Bull. no. 167, pp. 139-177. 346 Lindenschatt, S. M., Ueber den Einfluss der OH~ and H + ionen auf die Komplementablenkung und das differente Verhalten ver- schieden hoch erhitzter Sera bei der Komplementfixierung. Dissert. Heidelberg, 1913, pp. 1-39, quoted from Zentrbl. f. Biochem. u. Bio- physik., 1914, vol. 16, p. 504. 347 Markl, J. G., Ueber Saureagglutination von Pestbacillen, Centrbl. Bakt. Orig., 1915, vol. 77, pp. 102-108. 348 Meyer, K., Zur Kenntniss der Bakterienproteasen, Biochem. Zeitsch., 1911, vol. 32, pp. 274-279. Schmidt-Hoagland: Table of P H , H + and OH" Values 63 349 Michaelis, L., Die Saureagglutination der Bakterien, insbeson- dere der Typhusbazillen, Deut. med. Woeh., 1911, vol. 37, pp. 969-971. sso Michaelis, L., and Marcora, F., Die Saureproduktivitat des Bacterium coli, Zeitschr. f. Immunitatsfrseh. u. exper. Therap., 1912, vol. 14, pp. 170-173. 351 Miehaelis, L., and Skwirsky, P., Der Einfluss der Eeaktion auf die spezifische Hamolyse, Zeitschr. f. Immunitatsfrsch. u. exper. Therap,. 1910, vol. 4, pp. 357-374, 629-635. - 352 Michaelis, L., and Takahashi, D., Die isoelektrischen Konstan- ten der Blutkorperchenbestandteile und ihre Beziehungen zur Saure- hamolyse, Biochem. Zeitschr., 1910, vol. 29, pp. 439-452. sss Poppe, Dr., Die Saureagglutination der Bakterien der Para- typhusgruppe, Zeitschr. f. Immunitatsfrsch. u. exper. Therap., 1912, vol. 13, pp. 185-191. 354 Walbum, L. E., Die Bedeutung der Wasserstoffionenkonzen- tration fiir die Hamolyse, Biochem. Zeitschr., 1914, vol. 63, pp. 221- 268. 355 Waterman, H. J., Ueber einige Faktoren welche die Entwicke- lung von Penicillium glaucum beeinflussen. Beitrag zur Kenntnis der Antiseptica und der Narkose, Ceutrbl. f. Bakt., 2. Abt., 1915, vol. 42, pp. 639-688. IV. SOIL AND PLANT. sse Conner, S. D., Acid soils and effect of acid phosphate and other fertilizers upon them, Jour. Ind. Eng. Chem., 1916, vol. 8, pp. 35-40. SST Fischer, G., Die Sauren und Kolloide des Humus, Kiihn Arch., 1914, vol. 4, pp. 1-36. 358 Gillespie, L. J., The reaction of soil and measurements of hydrogen-ion concentration, Jour. Wash. Acad. Sci., 1916, vol. 6, pp. 7-16. sso Gillespie, L. J., and Hurst, L. A., Hydrogen ion concentration measurements of soils of two types: caribou loam and washburn loam, Soil Science, 1917, vol. 4, pp. 313-319. sso Haas, A. E. C., The acidity of plant cells as shown by natural indicators, Jour. Biol. Chem., 1916, vol. 27, pp. 233-241. ssi Haas, A. B. C., Eeaction of plant protoplasm, Bot. Gaz., 1917, vol. 63, pp. 225-228. 362 Haas, A. E. C., The excretion of acid by roots, Proc. Nat. Acad. ' Sci., 1916, vol. 2, pp. 561-566. ses Haas, A. E. C., Anesthesia and respiration, Science, n.s., 1917, vol. 46, pp. 462-464. 364 Hoagland, D. E., The effect of hydrogen and hydroxyl ion concentration on the growth of barley seedlings, Soil Science, 1917, vol. 3, pp. 547-560. ses Hoagland, D. E., and Sharp, L. T., Eelation of carbon dioxide to soil reaction as measured by the hydrogen electrode, Jour. Agr. Ees., 1918, vol. 12, pp. 139-148. see Miyake, K., Toxic action of soluble aluminum salts upon the growth of the rice plant, Jour. Biol. Chem., 1916, vol. 25, pp. 23-28. 367 Pantanelli, E., Ueber lonenauf nahme, Jahrb. wiss. Bot., Pringsheim, 1915, vol. 56, pp. 689-733. 64 University of California Publications in Physiology [VOL. 5 ses Plummer, J. K., Studies in soil reaction as indicated by the hydrogen electrode, Jour. Agric. Res., 1918, vol. 12, pp. 19-31. 369 Saidel, T., Quantitative Untersuchungen iiber die Eeaktion wasseriger Bodenausziige, Bull. Sect. Sci. Acad. Roumaine, 1913, Ann. 2, pp. 38-44. 370 Sharp, L. T., and Hoagland, D. R., Acidity and adsorption in soils as measured by the hydrogen electrode, Jour. Agric. Res., 1916, vol. 7, pp. 123-145. 371 Wagner, R. J., Wasserstoffionenkonzentration und natiirliche Immunitat der Pflanzen, Centrbl. f. Bakt., 2. Abt., 1916, vol. 44, pp. 708-719. V. MISCELLANEOUS. 372 Auerbach, F., and Pick, H., Die Alkalitat wasseriger Losungen kohlensaurer Salze, Arbeit, a. d. kais. Gesundheitsamte, 1912, vol. 38, pp. 243-274. 373 Bethe, A., Die Bedeutung der Elektrolyten fiir die rhythmisehen Bewegungen der Medusen, Angriffspunkt der Salze, Einfluss der Anionen und Wirkung der OH~ und H + lonen, Arch, f . d. ges. Physiol., 1909, vol. 127, pp. 219-273. 374 Bjerrum, N., Studien iiber chromichlorid, Zeitschr. f . phys. Chem., 1907, vol. 59, pp. 336-383. 375 Bjerrum, N., Studien iiber chromichlorid. Ill, Hydroxoaquo- chromichloride, Zeitschr. f. phys. Chem., 1910, vol. 73, pp. 724-759. 376 Brode, J., and Lange, W., Beitrage zur Chemie des Essigs mit besonderer Beriicksichtigung seiner Untersuchungsvcrfahren, Arbeit. a. d. kais. Gesundheitsamte, 1909, vol. 30, pp. 1-54. 377 Cohn, E. J., Relation between the hydrogen-ion concentration of sperm suspensions and their fertilizing power, Anat. Rec., 1917, vol. 11, p. 530. 378 Dale, D., and Thacker, C. R. A,, Hydrogen ion concentrations limiting automaticity in different regions of the frog's heart, Jour. Physiol., 1914, vol. 47, pp. 493-508. 379 Hildebrand, J. H., and Bowers, W. G., A study of the action of alkali on certain zinc salts by means of the hydrogen electrode, Jour. Am. Chem. Soe., 1916, vol. 38, pp. 785-788. sso Hildebrand, J. H., and Harned, H. S., The rapid determina- tion of magnesia in limestone by means of the hydrogen electrode, 8th Intern. Cong. Appl. Chem., 1912, vol. 1, pp. 217-225. ssi Jessen-Hansen, H., Influence de la concentration en ions hydro- gene sur la valeur boulangere de la farine, C.-R. Lab., Carlsberg., 1911, vol. 10, pp. 170-206. 382 Loeb, J., Ueber die Ursachen der Giftigkeit einer reinen Chlor- natriumlosung und ihrer Entgiftung durch K und Ca, Biochem. Zeitschr., 1906, vol. 2, pp. 81-110. sss Loeb, J., and Wasteneys, H., Die Beeinfliissung der Entwicke- lung und der Oxydationsvorgange im Seeigelei (Arbacia) durch Basen, Biochem. Zeitschr., 1911, vol. 37, pp. 410-423. 384 Michaelis, L., Die Saure- Dissoziationskonstanten der Alkohole und Zucker, insbeesondere der Methyl-glucoside, Ber. d. deut. chem. Ges., 1913, vol. 46, pp. 3683-3693. 1919] Schmidt-Hoagland: Table of P H , H + and OH- Values 65 sss Michaelis, L., and Eona, P., Die Alkaliempfindlichkeit des Traubenzuckers, Biochem. Zeitschr., 1910, vol. 23, pp. 364-369. 386 Paul, T., Der Sauregrad des Weines, Zeitschr. f . Eleetroehem., 1915, vol. 21, pp. 80-89. SST Sand, H. J. S., and Law, D. J., The employment of the electro- metric method for the estimation of the acidity of tan liquors, Jour. Soc. Chem. Ind., 1911, vol. 30, pp. 3-5. 388 Szili, A., Experimentelle Untersuchungen iiber Saureintoxika- tion, Arch. f. d. ges. Physiol., 1906, vol. 115, pp. 82-105. 389 Szili, A., Weitere Untersuchungen iiber Vergiftung mit an- organischen und organischen Sauren, Arch. f. d. ges. Physiol., 1909, vol. 130, pp. 134-155. 390 Wahl, E., New scientific conceptions and their application to quality and methods of preparing beer, Am. Brewers' Eev., 1915, vol. 29, pp. 271-274, 365-368, 557-559, quoted from Chemical Abst., 1916, vol. 10, p. 1398. 391 Walker, J., and Kay, S. A., The acidity and alkalinity of natural waters, Jour. Soc. Chem. Ind., 1912, vol. 31, pp. 1013-1016. 392 Wood, J. T., Sand, H. J. S., and Law, D. J., The employment of the electrometric method for the estimation of the acidity of tan liquors, Jour. Soc. Chem. Ind., 1911, vol. 30, pp. 872-877. VI. INDICATORS. 393 Acree, S. F., On the theory of indicators and the reactions of phthaleins and their salts, Am. Chem. Jour., 1908, vol. 39, pp. 528- 544. 394 Acree, S. F., and Slagle, E. A., On the theory of indicators and the reactions of phthaleins and their salts, Am. Chem. Jour., 1909, vol. 42, pp. 115-147. 395 Bogert, M. T., and Scatchard, G., Eesearches on quinazolines xxxiii. A new and sensitive indicator for acidimetry and alkalimetry, and for the determination of hydrogen ion concentrations between the limits of 6 and 8 on the Sorensen scale, Jour. Am. Chem. Soc., 1916, vol. 38, pp. 1606-1615. 396 Crozier, W. J., Some indicators from animal tissues, Jour. Biol. Chem., 1916, vol. 24, pp. 443-445. 397 Fels, B., Studien iiber die Indikatoren der Acidimetrie und Alkalimetrie II, Zeitschr. f. Eleetroehem., 1904, vol. 10, pp. 208-214. 398 Friedenthal, H., Die Bestimmung der Eeaktion einer Fliissig- keit mit Hilfe von Indikatoren, Zeitschr. f. Eleetroehem., 1904, vol. 10, pp. 113-119. 399 Harvey, E. N., A criticism of the indicator method of deter- mining cell permeability for alkalies, Am. Jour. Physiol., 1913, vol. 31, pp. 335-342. 400 Henderson, L. J., and Forbes, A., On the estimation of the intensity of acidity and alkalinity with dinitrohydroquinone, Jour. Am. Chem. Soc., 1910, vol. 32, pp. 687-689. 401 Hottinger, E., Ueber ' ' Lackmosol, ' ' den empfindlichen Be- standtheil des Indicators Lackmoid. Darstellung und einige Eigen- schaften, Biochem. Zeitschr., 1914, vol. 65, pp. 177-188. 402 Kelly, T. H., Hydrogen-ion acidity, Jour. Lab. Clin. Med., 1915, vol. 1, pp. 194-196. 66 University of California Publications in Physiology [VOL. 5 403 Lubs, H. A., and Acree, S. F., On the sulf onphthalein series of indicators and the quinone-phenolate theory, Jour. Am. Chem. Soc., 1916, vol. 38, pp. 2772-2784. 404 Lubs, H. A., and Clark, W. M., On some new indicators for the colorimetrie determination of hydrogen-ion concentration, Jour. Wash. Acad. Sci., 1915, vol. 5, pp. 609-617. 405 Lubs, H. A., and Clark, W. M., A note on the sulphone- phthaleins as indicators for the colorimetrie determination of hydro- gen-ion concentration, Jour. Wash. Acad. Sci., 1916, vol. 6, pp. 481- 489. 406 Micfiaelis, L., and Bona, P., Zur Frage der Bestimmung der H~ lonenkonzentration durch Indikatoren, Zeitschr. f. Electrochem., 1908, vol. 14, pp. 251-253. 407 Michaelis, L., and Kona, P., Der Einfluss der Neutralsalze auf die Indicatoren, Biochem. Zeitschr., 1909, vol. 23, pp. 61-67. 408 Noyes, A. A., Quantitative application of the theory of indi- cators to volumetric analysis, Jour. Am. Chem. Soc., 1910, vol. 32, pp. 815-861. 409 Palitzsch, S., Sur 1 'emploi du rouge de methyle au mesurage colorime'trique de la concentration en ions hydrogene, C.-E. Lab., Carlsberg, 1911, vol. 10, pp. 162-169. 410 Palitzsch, S., Ueber die Verwendung von Methylrot bei der colorimetrischen Messung der Wasserstoffionenkonzentration, Biochem. Zeitschr., 1911, vol. 37, pp. 131-138. 411 Eosenstein, L., The ionization constant of phenolphthalein and the effect upon it of neutral salts, Jour. Am. Chem. Soc., 1912, vol. 34, pp. 1117-1128. 412 Salessky, W., Ueber Indikatoren der Acidimetrie und Alkali- metrie I, Zeitschr. f. Electrochem., 1904, vol. 10, pp. 204-208. 413 Salm, E., Die Bestimmung des H+-Gehaltes einer Losung mit Hilfe von Indikatoren, Zeitschr. f. Electrochem., 1904, vol. 10, pp. 341-346. 414 Salm, E., Kolorimetrische Affinitatsmessungen, Zeitsehr. f Eleetrochem., 1906, vol. 12, pp. 99-101. 415 Salm, E., Studie iiber Indikatoren, Zeitschr. f. phys. Chem., 1906, vol. 57, pp. 471-501. 416 Salm, E., Messungen der Affinitatsgrossen organiseher Sauren mit Hilfe von Indikatoren, Zeitsehr. f. phys. Chem., 1908, vol. 63, pp. 83-108. 417 Salm, E., and Friedenthal, H., Zur Kenntnis der acidimetrischen und alkalimetrischen Indikatoren, Zeitschr. f. Electrochem., 1907, vol. 13, pp. 125-130. 418 Scatchard, G., and Bogert, M. T., A new and very sensitive indicator for acidimetry and alkalimetry and for determining hydro- gen ion concentrations between the limits of 6 and 8 on the Sorensen scale, Science, n.s., 1916, vol. 43, p. 722. 419 Sorensen, S. P. L., and Palitzsch, S., Sur un indicateur nouveau, o-naphtolphtaleine, ayant un virage au voisinage du point neutre, C.-E. Lab., Carlsberg, 1910, vol. 9, pp. 1-7. 420 Sorensen, S. P. L., and Palitzsch, S., Ueber den ' ' Salzfehler ' ' bei der colorimetrischen Messung der Wasserstoffionenkonzentration des Meerwassers, Biochem. Zeitsch., 1913, vol. 51, pp. 307-313. Schmidt-Hoagland: Table of P H , H + cmd OR- Values 67 421 Stieglitz, J., The theories of indicators, Jour. Am. Chem. Soc., 1903, vol. 25, pp. 1112-1127. 422 Thiel, A., Der Stand der Indikatorenfrage, Sammlung chem. u. chem.-tech. Vortrage, 1911, vol. 16, pp. 307-422. 423 Tizard, H. T., The colour changes of methyl-orange and methyl- red in acid solution, Jour. Chem. 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Bact., 1917, vol. 2, pp. 629-633. 43T Gainey, P. L., Soil reaction and the growth of azotobacter, Jour. Agric. Ees., 1918, vol. 14, pp. 265-271. 438 Gainey, P. L., Soil reaction and the presence of azotobacter, Science, n.s., 1918, vol. 48, pp. 139-140. 439 Gillespie, L. J., Correlation of H-ion exponent and occurrence of bacteria in soil, Science, n.s., 1918, vol. 48, pp. 393-394. 440 Gillespie, L. J., and Wise, L. E., Action of neutral salts on humus and other experiments on soil acidity, Jour. Amer. Chem. Soc., 1918, vol. 40, pp. 796-813. 68 University of California Publications in Physiology [VOL. 5 441 Gillespie, L. J., The growth of the potato scab organism at various hydrogen ion concentrations as related to the comparative freedom of acid soils from the potato scab, Phytopathology, 1918, vol. 8, pp. 257-269. 442 Goldberger, J., The change in the hydrogen-ion concentration of muscle during work, Biochem. Zeitschr., 1917, vol. 84, pp. 201-209, after Chem. 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UNIVEESITY OF CALIFORNIA PUBLICATIONS (Continued) 3. Can the Cerebral Cortex be Stimulated Chemically? . (Preliminary communication), by S. S. Maxwell. Pp. 17-19. February, 1906 06 4. The Control of Galvanotropism in Paramecium by Chemical Sub- stances, by Frank W. Bancroft. Pp. 21-23. March, 1906 10 5. The Toxicity of Atmospheric Oxygen for the Eggs of the Sea-urchin (Strfngylocentrotui purpuratvs) after the Process of Membrane Formation, by Jacques Loeb. Pp. SS-S7. March, 1906. 6. On the Necessity of the Presence of Free Oxygen in the Hypertonic Sea-water for the Production of Artificial Parthenogenesis, by Jacques Loeb. Pp. 39-47. March, 1906. Nos, 6 and 6 in one cover 18 7. On the Counteraction of the Toxic Effect of Hypertonic Solutions upon the Fertilized and Unfertilized Egg of the Sea-urchin by Lack of Oxygen, by Jacques Loeb. Pp. 49-56. April, 1906 .05 8. On the Production of a Fertilization Membrane in the Egg of the Sea-urchin with the Blood of Certain Gephyrean Worms (a pre- liminary note), by Jacques Loeb. Pp. 57-58. March, 1907 . .05 9. Note on the Synthesis of a Protein through the Action of Pepsin (preliminary communication), by T. Erailsford Robertson. Pp. 59-60. April. 1507 .05 10. The Chemical Character of the Process of Fertilization, and ita Bear- ing upon the Theory of Life-Phenomena, by Jacques Loeb. Pp. 61-80. September, 1907 " , 25 11. A New Proof of the Permeability of Cells for Salts or Ions (a pre- liminary communication), by Jacques Loeb. Pp. 81-86. January, 1908 . .05 12. The Origin of two new Retrogressive Varieties by one Mutation in Mice, by Arend L. Hagedoorn. Pp. 87-90. September, 1908 .05 IS. On Synthesis of Parunuelein through the Agency of Popsin and Chemi- cal Mechanics of Hydrolysis and Synthesis of Proteins through tha Agency of Enzymes, by T. B. Robertson. Pp. 91-94. Decembar, 1908 _ 05 14. The Inheritance of Yellow Color in Rodents, by Arend L. Hagedoorn. Pp. 95*99. March, 1909 06 15. Table of H + and OH- Concentrations corresponding to Electromotive Forces determined in Gas-chain measurements, by 0. L. A. Schmidt. Pp. 101-113. September, 1909 10 16. The Proteins, by T. Brailsford Robertson. Pp. 115-194. October, 1910 $1.00 17. Further Proof of the Identity of Heliotropism in Animals and Plants, by Jacques Loeb and S. S. Maxwell. Pp. 195-197. January, 1910 .05 Vol.4. 1. Experiments on the Function of the Internal Ear, by S. S. Maxwell. Pp. 1-4. September, 1910 05 2. On the Rise of Temperature in Rabbits, Caused by the Injection of Salt Solutions, by Theo. C. Burnett. Pp. 5-7. September, 1910 05 3. A Biochemical Conception of Dominance, by A. R. Moore. Pp. 9-15. September, 1910 _ 05 4. Galvanotropic Orientation in Gonium pectorale, by A. R. Moore and T. H. Goodspeed. Pp. 17-23. May, 1911 .05 5. On a Possible Source of the Biological Individuality of the Tissues and Tissue-fluids of Animal Species, by T. Brailsford Robertson. Pp. 25-30. May, 1911 05 6. Some Factors Influencing the Quantitative Determination of Gliadin, by J. E. Greaves. Pp. 31-74. August, 1911 40 7. Errors of Refraction Occurring in the Students of the University of California, by Theo. 0. Burnett. Pp. 75-77. August, 1911 05 8. On the Cytolytic Action of Ox-Blood Serum upon Sea-Urchin Eggs, and Its Inhibition by Proteins (Preliminary communication), by T. Brailsford Robertson. Pp. 79-88. February, 1912 10 9. On the Nature of the Cortical Layer in Sea Urchin Eggs, by A. R, Moore. Pp. 89-90. March, 1912. 10. On the Nature of the Sensitization of Sea Urchin Eggs by Strontium Chloride, by A. R. Moore. Pp. 91-93. March, 1912. Nos. 9 and 10 in one cover 05 11. On the Isolation of Ob'cytase, the Fertilizing and Cytolyzing Substance in Mammalian Blood Sera, by T. Brailsford Robertson. Pp. 95-102. March, 1912. 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