CHEMICAL COMPOSITION OF FOOt) -FISHES. 6 93 
(2) With a float, or, as is more convenient, a simple device such as a 
black and white reflecting surface of paper held behind the burette, and 
sights to insure that the level of the eye shall be the same as that of 
the meniscus, or, indeed, by using proper care without float or other 
help, reasonably accurate reading is easy even with burettes of ordinary 
width. 
(3) With very narrow burettes, well cleaned and provided with fine 
jets, it is easy without float, reflector, sights, or other helps for reading, 
to make measurements with a probable maximum error of *001 to .002 cc. 
in 10 cc. For accurate measuring of small quantities of solutions, 
therefore, the narrow burette is decidedly advantageous. 
In the determinations of nitrogen by the soda-lime method we have 
found it convenient to employ quite concentrated solutions of standard 
acid. For this we have, after some years’ experience, settled upon a 
10 cc. burette of about 5 mm. internal diameter graduated to .05 cc. 
For standard alkali, which we make more dilute, we employ a somewhat 
wider burette. Since the narrow burettes of ordinary thickness are apt 
to get broken, we find it advisable to have them made of thick glass. 
For the ordinary work of analysis, burettes of the usual width (when 
they are kept clean and when the measurements by which they are 
calibrated and those in the ordinary routine of analysis are made in the 
same way) give tolerably good results. It is only when especial accu- 
racy is desired that the narrow burettes and the precautions above sug- 
gested (regarding cleanness of the burettes and either slow drawing off 
of the solution through narrow jets or other means to avoid error from 
the afterflow) are needed. Of course, the greater dilution of solution 
which may be used in the wider burettes compensates more or less com- 
pletely for the larger error involved in their use. But where, for the 
sake of sharpness of the color reaction or for other reasons, as, for in- 
stance, to avoid pressure on the combustion tubes, it is desirable to use 
very small quantities of concentrated solutions, the narrow burettes 
offer decided advantages. 
. Since most of the analyses were made, the method of Kjeldahl has 
come into use, and is now employed in this laboratory in preference to 
the soda-lime method, though we find it advantageous to use the latter 
from time to time as a check. 
EATS, ETHER EXTRACT. 
The fats were extracted with ether, which, after various trials with 
chloroform, benzine, and carbon disulphide, we are persuaded is the 
most convenient solvent for the purpose. 
The determinations were made in the material which had been dried 
in hydrogen. Generally, from 0.3 to 1.0 grammes was used for the extrac- 
tion. The operation was conducted in an apparatus similar to that 
described by Johnson.* The corks and filter paper were always treated 
*Am. Jour. Sci., 13, 1887, 190. 
