NEW BOOKS Studien zur Lehre von den kolloiden Losungen. B J , T . Siedberg. (~Yova =Icta Regiae Socictutzs Sciriztinrnm 1-psaliciisis. So..I\-, 1-01. 2. S o . I.) 22 X 28 cni; p p , T i z - 1 6 0 . 1-psula: . l k a t l e m ~ s r l ~ cLizichdYuckeYu‘, rqo:.-Bredig’s method of olitaining colloidal metals by means of a n arc under the surface of a liquid n-orks xell with methyl alcohol and ethyl alcohol ; b u t with many organic solvents the liquid itself is decomposed and carbon is set free. The author connects his electrodes v i t h the secondary wires of a n induction coil and places a glass condenser in parallel with t h e m One electrode consists of granular metal or of metal strips. This apparently gives him a universal method I)>vhich a n y metal can be obtained in colloidal form, The disintegration is due to a n oscillatory arc discharge. The most favorable conditions a r c those in ~ I i i c hthe capacity is :is large as possible Ii-hile the self-induction. the ohmic resistance, and the length of spark are kept as small a s possible. I n the difiereiit groups of the periodic system the disintegration increases rapidly with increasing atomic veight. The deco~npositionof the liquid is greatest with the positi1-e metals such as calcium and magnesium : and with those xvhich have catalytic properties such a s cohalt, nickel, and platinum. One of the very interesting things in the paper is the account of the preparation of colloidal metals of the alkalies and of the alkaline earths. Ethyl ether and pentane xere used a s liquids in a n atmosphere of hydrogen. \\?th potassium, rubidium and caesium i t \vas necessary to Xvork a t temperatures approximating - 1 0 0 ~ C. “ I n the group, sodium, potassium, rubidium and caesium, there are some very interesting regularities. I n the first place, there are relations b e t ~ e e nthe atomic veight and the color of the colloidal solutions. \\’ith increasing atomic weight the color moves toward the red end of the spectrum. Colloidal sodium is violet-very like a solution of potassium permanganate-potassium is blue, rubidium blue with a touch of green, and caesium bluish-green, these colors being those of the smallest particles. I n the second place, the color depends on the size of the metallic particles. \Vith increasing coagulation the particles become larger and the color moves toward the red end of the spectrum. It has often been pointed out t h a t there is no simple relation between the size a n d the color of the particles. b u t i t seems to me t h a t in this case this relation is quite unmistakable. “There is also a surprising agreement between the color of the colloidal solution and t h a t of the metal a s vapor. I n the literature there are only brief and incomplete notes on the colors of the vapors of the alkali metals. I n fact, t h e color of caesium vapor is not a matter of record, so far a s I know. T h e agreement is very good for sodium and rubidium. Potassium vapor is bluishgreen a t low temperature and the larger particles of colloidal potassium are also bluish-green ; b u t the smallest particles of colloidal potassium are blue. It would be of great interest to determine the colors of the vapors of the alkali metals a t different temperatures, to determine the absorption spectra, a n d to compare these last with those of the colloidal solutions. -1determination of
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caesium vapor would be especially important as it would show whether t h e relations mentioned apply to this metal a s well. Of course there would b e serious difficulties i n carrying o u t such a n investigation for these vapors a t t a c k almost all vessels.” I n the second section of the volume, the author considers the question of stability and finds t h a t there are well-defined critical temperatures and t h a t these temperatures are raised by the addition of small amounts of a non-colloidal third substance. T h e third section deals with the Brownian movements. The author gives the particles a constant movement in one direction, thus changing the oscillations into a wave-form of curve. This simplifies the measurements and the author finds t h a t the velocity of the particles is about one hundred times t h a t of the electrical migration under a potential drop of one volt per centimeter. He therefore considers t h a t the Brownian movements cannot be the result of electrical phenomena. After considering other possibilities, the author decides t h a t the Brownian movements are due to the actual oscillations of the molecules a s required by the kinetic theory of gases. Whether one accepts this last conclusion or not, there is no question but t h a t this is a very important investigation, and one which reflects great credit Il‘ilder D . Bancrojt on the author. Oeuvres de Pierre Curie, PuhliBes p a r les Soins dc la Socidtd F r a q a i s e de Physique. 16 X 25 cm; p p . xrii + 6 2 1 . Paris: Gauthieu-1-illars, 1908. Price: @ p e r , 2 2 fruzcs.-This volume of six hundred pages contains the complete works of Pierre Curie. At first sight this does not seem a large o u t p u t for a n active scientific career extending over twenty-seven years ; b u t the work is not of a kind to be measured by pages. Xt no time did Curie have a large number of students or a n adequately equipped laboratory. XI1 his life he interested himself in difficult problems of such a nature t h a t the results of a great deal of v o r k could be presented in relatively few words. T h e work on crystallography and on radioactivity may serve a s an illustration. Then, too, Curie vias a man who thought long about a subject before he published a n y thing on it, and if some one anticipated him he did not publish at all. I t is a matter of opinion whether an intense yearning for perfection in each publication is a n unmixed blessing; b u t one cannot help admiring the man \Tho has it a n d who lives u p to i t in these days when so many of us go to the opposite extreme. Curie’s papers deal n i t h four general topics : crystallography ; reduced equations; magnetism; and radioactivity. T h e last group is the one which has attracted t h e most attention and on which Curie vias working when his career was c u t s h o r t ; b u t i t would be a great mistake to consider the earlier work as unimportant. To take b u t a single instance, the paper on the magnetic properties of substances a t different temperatures is a masterly piece of work and will some d a y receive a great deal more attention than has y e t been bestowed upon it. T h e whole world is familiar with the details of Curie’s untimely d e a t h ; b u t i t h a s not known until now, about his unsatisfied longings for more adequate facilities. It is pathetic the way i n which Curie vias offered decorations when 1l;ilder D . Baiicrojt what h e wanted was a laboratory.
