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lengthen the life of man, while, when used as a bleaching agent 

 in the laundry, it shortens the life of his collars and shirts. 

 Amongst its uses may be mentioned the bleaching of cotton, linen 

 and paper-pulp. This compound is one of those I had in mind 

 when, at the beginning of the lecture, I said that in some of the 

 compounds of calcium used in the arts and industries the calcium 

 is only a junior partner. I mean that in the industrial uses of 

 -chloride of lime the valuable properties are due to the chlorine 

 rather than to the lime. The function of the latter is to reduce the 

 chlorine to a convenient and manageable form. There are many 

 cases in which lime or chalk is used in preparing some substance 

 which, in its finished state, contains no calcium. Such uses of lime 

 are, however, very important, as it would not be possible to find 

 .any other substance which could conveniently be substituted. 

 Take, for instance, the well known vegetable acids, citric, tartaric 

 and oxalic. The first of these is made from the juice) of the lemon 

 and the lime fruit. The name of the latter, by the way, is only 

 by accident spelt and pronounced like that of calcium oxide. 

 Lime, as the nam© of a fruit, may be regarded as a variant of the 

 word lemon, both being derived from the same Persian word. 

 Lime, as the name of the base of chalk, is of quite different origin 

 and is related to our own word " slime." Its primary application 

 seems to be to things that are sticky or pasty, and it was probably 

 given to the substance now called lime because of its use in 

 making the mortar which serves to stick together bricks, stones 

 and other building materials. To return to citric acid. The juice 

 of the fruit is boiled and filtered and powdered chalk added to the 

 still boiling liquid. Insoluble calcium citrate is formed and from 

 this free citric acid can easily be obtained. Tartaric acid is made 

 hy a somewhat similar process from the crude cream of tartar that 

 Is deposited from grape juice during its conversion into wine by 

 fermentation. In this case, however, another calcium compound 

 is used in addition to chalk. This other compound, calcium 

 •chloride, is quite different from " chloride of lime " as bleaching 

 powder is sometimes called. 



The frequent occurrence in plants of calcium oxalate was men- 

 tioned by our President in an earlier lecture of the course, but 

 these natural oxalates are not used as a source of oxalic acid on 

 the commercial scale. When sawdust is made into a paste with a 

 strong solution of potash and soda and then baked a large yield 

 of the oxalates of these alkalies results. These salts are converted 

 Into calcium oxalate by boiling with lime and water and the free 

 oxalic acid can then easily be obtained. 



One other use of lime in connection with vegetable acids may 

 he quoted here. At one stage of the preparation of acetic acid the 

 crude liquid obtained by distilling wood is neutralised with lime. 



In some cases lime is used in quickening up the pace of some 

 chemical action which it is desired to bring about. Thus, by add- 

 ing a little lime to animal fats, such as tallow or the refuse fat 

 from butchers' shops, and then treating the fats with steam under 



