CLEANING GLASSWARE 329 



water has been found ample to prevent the disturbance due to 

 lime in the water used. 



Hot water is necessary to be added to the test bottles. If it 

 is impossible, or exceedingly difficult to get good hot water where 

 needed, any water may be made hot by the addition of a quantity 

 of testing acid equal to about one-quarter of the volume of water 

 used. The acid will make the water hot, yet will not produce 

 any undesirable effects in the test. The writer has often em- 

 ployed this method of securing purified hot water where ordi- 

 nary hot water could not be obtained. 



It is necessary too, for best work, that the water be clean of 

 the ordinary organic impurities, such as would be introduced by 

 using an uncleaned pipette for the addition of the water to the 

 test. Milky water thus added produces a dull gray cloud below 

 or through the fat, and to that extent renders the read- 

 ing unreliable. 



Cleaning Glassware. — The glassware used in testing is not 

 difficult to clean if the washing is done at once, while everything 

 is fresh, but if the milk is allowed to become dry in the pipette, or 

 the residue of the test has been allowed to harden in the test bot- 

 tle the cleaning process will be many times more difficult. 



The first and most important step in the cleaning of the bot- 

 tles is to empty them while they are still hot and to shake the con- 

 tents vigorously so that the gray-white sediment noticeable in the 

 bottom of the bottle will be thoroughly removed. The sediment 

 referred to is the milk ash. It is insoluble in water and if per- 

 mitted to dry and harden in the bottom will be difficult to 

 remove, but may very easily be shaken out while the sample is 

 fresh. All the bottles to be washed should then be rinsed, set up- 

 right and into them sprinkled a quantity of strong washing pow- 

 der. Water as hot as the hands can bear should then be intro- 

 duced and the neck cleaned inside and out by means of a cyl- 

 indrical bottle brush made for the purpose. After being thus 

 cleaned all the glassware should be rinsed well with hot water to 

 give the glass a gloss and a clean feel. 



Ordinary soap should not be used in the cleaning of such 

 glassware, as the chemical action which takes place with the 

 sulfuric acid and the ingredients of the soap is such as to 



