66 Domestic Science 



37. A further method of determining the density or 

 the specific gravity of solid substances will be found fully 

 described in Chapter vi. We will next consider a simple 

 method of determining the density of a liquid substance. 



EXPERIMENT 20. Counterpoise carefully (p. 57) a 

 small long-necked flask with a narrow strip of paper 

 gummed along its neck, a horizontal line being drawn 

 across the paper at any point. Pour some of the liquid of 

 which the density is required into the flask till the lower 

 edge of the meniscus just touches the mark on the paper 

 strip. Weigh the liquid by adding weights to the other 

 pan. Pour out the liquid and wash out the flask with 

 several successive quantities of tap -water to ensure that 

 no appreciable amount of the liquid originally present 

 remains in the flask. Rinse the flask out twice with 

 small quantities of distilled water, pour in distilled 

 water till the mark on the neck is reached as before, 

 and wipe the outside of the flask quite dry. Weigh the 

 distilled water. 



Since 1 g. of distilled water at ordinary temperatures 

 occupies almost exactly 1 c.c., the number of grams of 

 water contained in the flask is the same as the number 

 of c.c. in the interior volume of the flask up to the 

 mark. The liquid and the water both occupied this 

 volume, hence the volume of the liquid is known. The 

 mass of the liquid having been already determined, its 

 density is a matter of simple calculation. 



Exercise for Student. 



What is the specific gravity of the liquid of which you have 

 just determined the density ? 



38. To save time in the determination of liquid 

 densities, small flasks are constructed to hold, at 

 ordinary temperatures, a known weight say 10, 25, 



