January 24, 1908] 



SCIENCE 



145 



THE NEW YORK ACADEMY OF SCIENCES — SECTION 



OP ASTRONOMY, PHYSICS AND 



CHEMISTRY 



At a meeting of tlie section held on Mon- 

 day, October 21, at the American Museum of 

 Natural History, three papers were read. 

 The Selective Reflection Characteristic of 



Salts of Carhonic and Other Oxygen Acids: 



L. B. Morse. 



I. The Selective Reflection of Carlonates as 

 a Function of the Atomic Weight of the Base. 

 ■ — Polished plane surfaces of (Mg, Ca, Fe, Mn, 

 Zn, Sr, Ba and Pb) CO3 were prepared and 

 the ratio of the reflected to the incident radia- 

 tion was measured at short wave-length in- 

 tervals between 4 fx, and 15 ju. The following 

 are the principal conclusions reached: 



1. The reflection curves for all the carbon- 

 ates examined show between 4 ju and 15 //, three, 

 and only three, bands of abnormal reflection. 

 Abnormal reflection interpreted means a free 

 resonance period of the molecule. 



2. The bands fall into three separate and 

 definite spectral regions, which are distinct 

 from the regions where the salts of other acids, 

 so far as known, show reflection maxima. 



3. With few exceptions, an increase in the 

 atomic weight of the base causes a shift of all 

 three reflection maxima toward long waves by 

 an amount roughly proportional to the change 

 in atomic weight of the base. 



This is shown for the first reflection band by 

 curve A, Fig. 1, in which the atomic weights 

 of the bases are plotted as ordinates, and the 

 wave-lengths of the " flrst " reflection maxima 

 as abscissae. 



II. The Role Played hy Oxygen in the 

 Selective Reflection of Carbonates, Nitrates, 

 Sulphates and Silicates. — Combining with the 

 data on carbonates the scattered observations 

 of other observers on nitrates, sulphates and 

 silicates, the tentative hypothesis has been 

 made that the oxygen atom is the one chiefly 

 responsible for the marked reflection observed. 



The wave-lengths of the first reflection bands 

 in CaC03, KNO,,^ CaSO, and MgSiO/ are 



' Two values are plotted for KNO3 correspond- 

 ing to the results obtained by two independent 

 observers, Pfund and Coblentz. 



" If a correction be applied to correct for Mg 



plotted as abscissae, curve h. Fig. 1, and as 

 ordinates the weights of the acid-forming 

 elements combined with O3 (0 = 12, N ^ 14, 

 |S = 24, and Si = 28). 



50 



R-<i 



7 

 i. 



« 



Y 



The lines drawn show clearly that a small 

 increase in the weight of the acid-forming ele- 

 ment produces a much greater displacement of 

 the reflection band than does the same increase 

 in the weight of the base, and this is in full 

 agTeement with the chemist's view of the rela- 

 tive strength of the bands existing between the 

 acid-forming element and oxygen, and that be- 

 tween the hase and oxygen. 



The results suggest a new and far-reaching 

 method by which it may some time be possible 

 being lighter than Ca, this would bring the MgSiOa 

 point even nearer the line drawn. 



