FOOD MATERIALS AND HOW TO DETECT THEM 29 



and keep it there until all water has been driven off. To 

 determine this, weigh from time to time, noting decrease 

 until the weight becomes constant. 



How much water does each article contain ? 



Note. Care should be taken not to heat the substance so hot 

 as to set it on fire. The substance should be dried and not charred. 



15. MINERAL SALTS 



Object. To prove that there is mineral matter in food 

 stuffs. 

 Apparatus. Same as in Experiment 14. 



Method. After the water has been driven off as in the 

 preceding Experiment, continue the heat until no gases come 

 off. Then increase the heat and burn up the contents of 

 the tube. If nothing remains, it is a sign that no mineral 

 matter is present ; but if ashes are left in the tube, it is an 

 indication that mineral matter is there. 



Substances like alcohol, ether, chloroform, benzine, gaso- 

 line, etc., leave no ash, therefore they are said to contain 

 no mineral matter. 



Conclusion. State in one sentence how the presence of 

 mineral salts is detected in foods. 



