NO. 5 



HYDROGEN CYANIDE RRACKETT AND LIDDEL 



lengths, however, were made mostly on a much wider spread, in- 

 ckiding simply the region from i/x to 2/i. A typical plate at this spread 

 of the same cell length is shown in figure 3. Figure 4 shows an 



Fig. 3. — Energy transmission curve showing absorption spectrum of 5 cm. 

 cell of liquid HCN at high dispersion. Slit width approx. 9.A. 



analysis of the bands in this region, the frequencies of the maxima 

 being plotted against percentage absorption. Table i gives the sum- 

 mary of the data obtained. The values of the fundamentals in vapor 

 are inserted for comparison since no liquid values have been obtained 



5000 6000 7000 8000 9000 10000 1 1000 /2000 cm" 



Fig. 4. — Diagrammatic representation of absorption ma.xima observed with 

 assignments of designations. Broken Hues show vapor absorption. Fre- 

 quency is plotted against per cent absorption. 



in that region. Intensity values, both as to percentage absorption and 

 absorption coefficient are only approximate. Generally the estimated 

 uncertainties in the frequency values indicated arise from the diffi- 

 culty of setting upon broad absorption maxima like those showni in 

 figure 3. Still less favorable are the conditions of the values for 4i'i 

 and 3i'i + i'2. which were obtained on a low spread plate such as that 

 shown in figure i. In other cases the larger uncertainties indicated 

 arise from the proximity of strong absorption bands. It will be seen 

 that the observed values of Av lie well within the probable values to 

 be expected, taking into account the normal variation to be expected 

 in the successive differences, together with the probable uncertainty 

 of measurement. The agreement certainly excludes any uncertainty 

 as to identification. Not only do the wave lengths lead definitely to 



