TECHNICAL CHEMISTRY. 443 



bearing trees are now being cultivated in the more easily inhabitable 

 portions of the tropics, it will be a long time before this source of 

 supply is an important factor in the market. And thus it comes that 

 the synthesis of india rubber presents to-day, from at least the technical 

 side, one of the most promising problems in chemistry. 



The investigation of india rubber is greatly handicapped by the 

 fact that it exists only in the colloidal state. The difficulties are per- 

 haps more largely physical than chemical; that is, it is the molecular 

 aggregation rather than the atomic structure of the individual mole- 

 cule which presents such almost insurmountable difficulties. There 

 are no clearly defined melting points, boiling points, tendencies to 

 crystallize or any of those means of separating mixtures or char- 

 acterizing individuals which aid in the investigation of most organic 

 compounds. The researches of Weber and Harris, resulting in the 

 establishment of the much needed methods of analysis, have been of 

 incalculable advantage to all those working with either the raw or the 

 manufactured article. In many directions also the paths along which 

 important results are to be obtained have already been blazed by these 

 investigators. Probably no other field presents such difficulties of 

 manipulation in addition to such profound problems of organic chem- 

 istry as does the investigation of india rubber; but on the other hand 

 few such unlimited opportunities for valuable work are offered in the 

 field of chemical research. 



Under the general head of utilization of trade wastes may be con- 

 sidered a large number of technical problems the solution of which 

 would not only add wonderfully to the economic resources of the 

 country, but would aid in the solution of that much vexed question, 

 river pollution. We have already mentioned the soda and sulphite 

 liquor resulting from the manufacture of cellulose fiber from wood. 

 Of almost equal importance is the waste yeast which is daily produced 

 in the brewing of beer and ale. An extract of this yeast has a food 

 value as shown by analysis equal to the best meat extracts. As the 

 quantity of yeast allowed to go to waste is from one to two pounds for 

 every barrel of beer brewed, we can form estimates of the great amount 

 of this material at hand. Arsenic sulphide from the purification of 

 crude acids, grease from the washing of wool, the utilization of city 

 garbage and many other problems of this order are everywhere in 

 evidence. It is not within the compass of this discussion to mention 

 these almost innumerable sources of manufacturing waste which exist 

 in the chemical industry; but keen competition on the one hand and 

 the state boards of health on the other are constant stimuli to increased 

 effort towards their utilization. 



Although I have endeavored to select the above examples of un- 

 solved problems with a view to touching upon as large a portion of 



