CIIKMISTKY. 



77 



not cause a dry mixture of carbonic oxide and 



:t tn explode ; curium. phosphorus, and sul- 

 jihur will iu)t imiif with dry oxygen ; and as 

 chemical science progresses we muy find (hut, 

 many well-known net inns arc conditioned by 

 the presence of minute (races c>l' oilier matter 

 which have hitherto escaped detection. We all 

 know the picfound alterations of the properties 

 of substance^ I iy minute traces of impurities; 

 h-s than one tenth per cent, of phosphorus \\ill 

 render steel unfit for certain purposes. The 

 supphire ami ruby differ from colorless alumina 

 only by the presence of traces of impurities 

 hardly recognizable by chemical analysis. 



The solutions of colloid substances, such as 

 albumen, silicic acid, tungstic acid, etc., are sup- 

 posed to differ in their nature from solutions of 

 crystalloid substances, (iraiium, in his paper on 

 that subject, defines the differences between crys- 

 talloid and colloid substances solutions of the 

 latter not. passing through the pores of certain 

 animal membranes and parchment paper, while 

 solutions of crystalloids pass freely through 

 them and suggested that the basis of the colloid 

 state might lie in the complex character of the 

 molecule. The facts that the solutions of colloid 

 substances do not have an appreciably higher 

 boiling point than water, or a lower freezing 

 point, and that in dissolving a colloid no change 

 of temperature takes place, or at least only a very 

 slight change, are regarded by C. E, Linebarger 

 a- indicating that a colloid solution is not a solu- 

 tion in the ordinary sense of the term, but rather 

 a mechanical mixture, an emulsion, the colloid 

 being held in a state of suspension in the water. 

 The same opinion has been reached by other 

 authors. Selecting from among the simplest and 

 stablest colloids. Mr. Linebarger, in order to ob- 

 tain results that may throw light upon the na- 

 ture of colloid substances in solution, has made 

 some determinations of the osmotic pressure of 

 solutions of colloid tungstic acid. The results 

 of the experiment gave a pressure corresponding 

 to a molecular mass for colloidal tungstic acid of 

 about 1,700, or nearly seven times 250, showing 

 the colloidal molecule to consist of seven simple 

 molecules. All the phenomena exhibited by col- 

 loids may be easily explained on the assumption 

 that the colloid molecule is very large. A solu- 

 tion of a colloid docs not seem to lower the freez- 

 ing point or raise the boiling point, because the 

 molecular mass is so great that it has but little 

 influence. A colloid solution might be regard- 

 ed as a step between a true solution and a true 

 emulsion. The colloid molecule is so much larger 

 than the water molecule that it stands to reason 

 that the properties of colloid substances must 

 differ in a marked degree from solutions of sub- 

 stances that possess a molecule much less heavy 

 than water. The ease with which colloidal sub- 

 stances are coagulated, or pass into the solid 

 state, indicate that there exist in the solution 

 molecular groupings similar to those existing in 

 a solid. 



In an address on Recent Advances in " Phys- 

 ical Chemistry." Prof. W Ostwald mentions it 

 as remarkable that the efforts of the investi- 

 gators who have been trying to determine the 

 value of the fundamental constant of the re- 

 lation of the atomic weight of oxygen to that of 

 hydrogen to within one part per thousand have 



not yet met with a generally accepted success. 



The question of the significance and numerical 

 values of the atomic- weights has made no prog- 

 ress of importance since the fundamental re- 

 searches of Lothar Meyer and Mendeleeff. Spec- 

 ulations do not cease in the direction given by 

 the assumption of the compound nature of the 

 elements, but there are none of which growth 

 and development can be prophesied. No new 

 elements of importance have recently come to 

 light. In the theory of gases, the investigations 

 continue according to the general equation of 

 condition, in that the recognition is steadily 

 breaking its way that the nearest entrance to the 

 theory of liquids leads necessarily over the crit- 

 ical point. The kinetic hypothesis is showing 

 itself here essentially unfruitful. The stoichi- 

 ometry of the liquid organic compounds, founded 

 by Hermann Kopp, has enjoyed a steady develop- 

 ment. While the question of the boiling point 

 seems to be essentially postponed until the gen- 

 eral theory of liquids becomes known, that of 

 the molecular volumes has reached a stage which 

 already assures the prospect of a successful period 

 of development. The additive scheme, according 

 to which the molecular volume is the sum of the 

 atomic volumes, determines only the roughest out- 

 lines of the phenomena; other factors make them- 

 selves everywhere felt ; and we must, more than 

 ever before, recognize the molecular volume as a 

 constituent property. In relation to the connec- 

 tion between the different properties of sub- 

 stances, a fruitful line of thought has been car- 

 ried out by Philippe-Guye, who has verified the 

 existence of a close connection between the crit- 

 ical constantsand the molecular refraction. Spec- 

 trum analysis has recently raken a promising 

 start in the stoichiometric direction. The view 

 now held as " an undoubted dogma," that at the 

 highest temperatures all compounds must be dis- 

 sociated into their elements, is regarded as " not 

 justified." " What we do know about the stability 

 of compounds is ... that all compounds which 

 are formed with absorption of heat become more 

 stable with rising temperature, and the reverse." 

 Because the majority of the compounds known 

 to us are formed from the elements with evolu- 

 tion of heat, and consequently become more un- 

 stable with rising temperature, the conclusion 

 has been drawn that this is in general the case. 

 From certain facts we may infer that the spectra 

 occurring at high temperatures may, under proper 

 conditions, belong to compounds which, formed 

 with great absorption of energy, may have a fleet- 

 ing existence confined to those temperatures. 

 From this point of view many difficult facts of 

 spectroscopy and spectrometry would have some 

 prospect of a proper interpretation. But little 

 is known as yet about the- connection between 

 color and constitution. The investigations of 

 Kriiss, Liebermann, and Vogel indicate that the 

 property is in great measure constitutive, becom- 

 ing additive only within the narrowest limits of 

 closely related compounds. The constitutive 

 character of the rotation of the plane of polariza- 

 tion has been always known and recognized. 

 Since Van 't Hoff and Le Bel pointed out the 

 connection between this property and the presence 

 of an " asymmetrical " carbon atom, this idea has 

 had an important development. The presence of 

 optical activity is now held as proof of the pres- 



