Am .  J  our.  Pharm .  \ 
August,  1901.  / 
Polai'ization  by  Mixtures. 
369 
The  amount  of  rotation  was  next  observed,  and  the  tube  unsealed 
at  one  end  and  cut  down  about  1  cm.,  refilled,  and  the  process 
repeated.  Observations  for  twelve  lengths  of  tube  were  taken,  and 
when  plotted  with  the  corresponding  rotations,  gave  a  fairly  straight 
line,  but  the  results  were  not  considered  sufficiently  accurate. 
In  order  to  obtain  the  best  possible  results,  a  series  of  tubes,  six- 
teen in  number,  was  constructed,  differing  from  each  other  by 
irregular  intervals  of  length.  These  could  be  tested  repeatedly 
and  afforded  a  check  on  the  work.  To  find  their  lengths,  measure- 
ments were  taken  on  two  sides  and  the  mean  taken.  The  following 
table  will  show  the  method  of  procedure : 
TABLE  I.— LENGTH  OF  TUBES. 
No.  of 
Tube. 
Length 
of  a  b. 
Length 
of  a'  b'. 
Mean 
(weight  1). 
Length 
of  a  b. 
Length 
of  a'  V. 
Mean 
(weight  2). 
Final 
Average. 
Cm. 
Cm. 
Cm. 
Cm. 
Cm. 
Cm. 
Cm. 
1 
0-44 
0-41 
0*425 
o*43 
0-41 
0-420 
0-42 
2 
076 
0-85 
0-805 
o-86 
0-76 
o'8io 
o-8i 
3 
1*04 
I'OO 
ro2o 
i'oi 
s'04 
1 '025 
1-02 
4 
1 '47 
1 '34 
1*405 
1*45 
1*32 
i*385 
i*39 
5 
178 
1*90 
1-840 
1-90 
i*77 
1*835 
1-84 
6 
3"42 
3-48 
3*45° 
3*41 
3*48 
3*445 
3*45 
7 
5*" 
5-20 
5*155 
5-20 
5*io 
5*i55 
5*15 
8 
6 '43 
6-5i 
6-470 
6*5i 
6-42 
6.465 
6*47 
9 
8-16 
813 
8-145 
8-i6 
8-n 
8-135 
8-14 
10 
9-84 
9-72 
9*78o 
972 
9-80 
9-760 
9'77 
11 
"•54 
11*57 
n'555 
11-57 
11-52 
ii*545 
11*55 
12 
13*27 
1 3  "3° 
13*285 
13*30 
13-27 
*3'285 
13-29 
13 
15*05 
- 
15*15 
15*085 
*5"*3 
15-08 
15-105 
15-10 
14 
16-89 
16-85 
16-870 
16-82 
16-88 
16-850 
1 6 -86 
15 
1838 
18-41 
l8*395 
18-41 
18-38 
i8-395 
18*40 
16 
19-63 
19*75 
19-690 
i9'75 
19-61 
19-680 
19-68 
The  next  table  shows  the  amount  of  rotation  afforded  by  a  solu- 
tion of  glucose  in  each  tube.  The  table  is  printed  in  full  in  order 
to  show  the  degree  of  precision  obtained  in  making  the  readings. 
