CHEMICAL INDUSTRY IN KWANGTUNG PROVINCE 141 



process, in the preparation and purification of many chem- 

 icals such as acetic, citric, oxalic; and tartaric acids, 

 potassium chlorate, caustic soda and potash, etc., for purify- 

 ing illuminating gas and sugar solution; in bleaching and 

 dyeing cotton; in tanning; in glass making; in metallurgical 

 operations; for disinfecting, etc. 



In Kwangtung lime is used only for mortar and cement 

 mixing, and in bleaching and dyeing work, in glass making 

 and for disinfecting. 



Lime for mortar and many other purposes is always 

 slaked immediately before use. 



As a rule 100 catties of good lime stone yield about 60 

 catties of lime. 



T'ung Oil ffl vfl. T'ung Oil which is generally known 

 as "Chinese Wood Oil" is made in Canton. It has been 

 known in America since 1896. It cannot be used in its raw 

 state, but must always be heated to a temperature of over 

 500 deg. F. It makes a very water-proof material. It is 

 obtained from the seeds of aleurites cordata, a tree which 

 grows in South and North China and in Japan. 



The seeds are usually roasted, broken into powder and 

 pressed as is the case with peanut oil- The cold pressed oil is 

 pale yellow, and is known in the trade as "White Tung Oil." 

 That resulting from hot pressing is dark in colour, and is 

 termed "black tung oil." The raw oil has a peculiar odor 

 suggestive of ham. 



Tung Oil is used principally in the manufacture of 

 varnishes and linoleum. When it is made with ordinary 

 resin, and suitably thinned, a varnish is obtained which is 

 not affected readily by water, while varnish made with resin 

 and linseed oil alone is quickly turned white by contact with 

 water. In consequence of this behavior of tung oil, it has 

 become very popular with the varnish maker as a means of 

 producing cheap but good varnish. 



Chinese Vermilion. — Chinese vermilion is made in 

 Wing Kat & tf in Canton. It is the finest quality of 

 vermilion, and its manufacture was long kept a secret. It is 

 known to be made by heating mercury and sulphur together 

 in shallow iron pans until they combine to form a black 

 mercuric sulphide. This is pulverized, and put into retorts 

 in small amounts at a time. The larger part of the black 

 sulphide sublimes into the upper part of the retort as a 

 bright red powder. This is ground, washed and dried. 

 Owino- to the patience and care exercised by the Chinese 

 workmen, a very fine product is obtained. 



Vermilion is very expensive and is a very heavy, opaque 

 and brilliant pigment. It is permanent, and not readily 



