134 



VOLUMETRIC AND INDIRECT ESTIMATION OF FAT. 



to stock bottle must not be more than -J of the capacity of the 

 burette. 



2. The bottom of the stock bottle must be well above the top 

 of the tube leading into the air chamber. 



The tube leading into the air chamber must be adjusted to the 

 mark on the burette equal to its capacity. 



The burette is used as follows : The tap is turned so that 

 the liquid enters and fills the burette. As it reaches the upper 

 portion, it passes up the tube and overflows into the air chamber 

 from which it is forced up the tube leading to the stock bottle. 

 When the liquid reaches a height corresponding to the level of 

 the liquid in the stock bottle, the liquid ceases to run, and the 

 burette is automatically filled to the zero point. When the 

 tap is turned the liquid runs out, air bubbling in from the stock 

 bottle, and measured quantities may be taken. After the liquid 

 has been run out as far as desired, the tap is turned, and the liquid 

 enters the burette. 



The liquid in the air chamber is forced back into the stock 

 bottle, and the burette automatically fills itself. 



The burette can be made of 9 c.c. capacity, but it is much 

 quicker to employ a graduated burette of much larger capacity 

 than any form of automatic measuring apparatus. 



The advantages claimed for the burette are 



(1) Automatic filling to zero point. 



(2) One turn of the tap only required to fill and to measure. 



(3) Impossibility of spilling corrosive liquids. 



(4) Saving of time, as the filling is done while other operations are 

 conducted. 



Chemicals. Commercial sulphuric acid containing 96 per 

 cent. H 2 S0 4 , which has a specific gravity of 1-842 at 15-5 C. 

 (60 F.). Owing to the fact that strong sulphuric acid has a 

 somewhat anomalous specific gravity, it is not advisable to test 

 the specific gravity directly. The following test will give good 

 results : Measure accurately 200 c.c. of acid into a large flask, 

 and to it add cautiously 15 c.c. of water, cooling the flask by 

 immersion in cold water. Take the specific gravity of this 

 diluted acid, either with an accurate hydrometer or by other 

 means. If the temperature be not exactly 15-5 (60 F.), add on 

 0-001 for each degree Centigrade above 15-5, or 0-00056 for each 

 degree Fahrenheit above 60F.(or subtract for temperatures below). 



The following table will give the strength of acid : 



Per cent. H 2 S0 4 . 

 98 (94-20) 



Specific Gravity of 

 Diluted Acid. 

 1-8380, 



1-8349, 

 1-8311. 



1-8268, 

 1-8217, 



97 (93-22) 



96 (92-24) 



95 (91-2I5) 



94 (90-28) 



