302 SCIENCE OF COMMON THINGS. 



"What is starch ? How manufactured ? 



PART IX. 



FAMILIAR CHEMISTRY. 



1943 What is starch f 



The name starch is given to a mealy substance which 

 is deposited in most vegetables at the time of ripening, 

 from the juices with which the cells of the plants are 

 filled. 



1944 What common vegetable especially abounds in starch f 



The potato ; which consists entirely of cells filled 

 with starch and water. 



A cell is a little membranous bladder filled with a solid or fluid sub- 

 stance. 



1945 Why does the laundress find it necessary to boil starch before 

 using it for stiffening linen, etc. f 



The starch, consisting of little granules, is insoluble 

 in cold water ; but when acted upon by hot water, 

 the granules burst and allow their contents, which are 

 soluble, to become mingled with the water. 



Starch is manufactured as follows : 



Potatoes, for example, from which most of the starch of commerce is 

 manufactured, after being pared, are grated to a pulp. This pulp is put 

 upon a sieve and stirred about, while at the same time a little stream of 

 water is made to flow upon it. A milkj r liquid runs through the sieve, 

 but the fibrous portion of the potato, the vegetable tissue, remains behind. 

 This liquid, after a short interval, deposits a white powder, which is the 

 starch. By the simple process of tearing up the vegetable tissue, and 

 removing the inclosed starch by washing, this substance may be procured 

 from a great variety of plants. 



1946 Why do potatoes, beans, rice, and most of the common vegetables, 

 swell up when boiled with water f 



Because the starch absorbs water at the boiling tern- 



