xxviii GENERAL SUMMARY OF SCIENTIFIC AND 



have clearly traced the successive stages in the formation of 

 chloral, and have shown that its hydrate is really the glycol 

 of ethylidene. O'Sullivan has examined the conditions un- 

 der which dextrine is produced from starch, and has prepared 

 it pure for the first time. He acted upon the starch both by 

 diastase and by acids. He has also shown that the pro- 

 longed action of malt upon starch really does produce the 

 sugar called maltose by Dubrunfaut. It has a specific rota- 

 tory power of +150, and reduces only two thirds as much 

 copper oxide as dextrose, into which it is converted by the 

 action of acids. It has the composition of a simple sugar. 

 Musculus using an ingenious method of dehydratation by 

 means of alcohol has succeeded in abstracting a molecule of 

 water from one of dextrose, and in producing a substance 

 closely resembling dextrin, though it has a less rotatory pow- 

 er. When we remember that the removal of one molecule 

 of water from two molecules of a simple sugar like dextrose 

 produces a compound sugar like cane sugar a synthesis of 

 vast importance, which is yet unaccomplished any steps 

 taken in this direction deserve notice. Kekule's remarkable 

 theory of the constitution of the aromatic series of organic 

 bodies, has received important verification in the discoveries 

 of the year. He, himself, has added to the idea of position 

 contained in it, and Hubner has fully confirmed the supposi- 

 tion that the six atoms of carbon in the nucleus are of equal 

 value. As a direct outgrowth of this theory, Graebe and 

 Liebermann produced alizarin from anthracene. And now 

 Emmerling and Engler have succeeded in the synthesis of in- 

 digotin, the coloring matter of indigo. Though by the proc- 

 ess of these chemists the yield is inconsiderable, yet their 

 solution of the true constitution of indi^o-blue will undoubt- 

 edly soon lead to other and, commercially, more valuable syn- 

 theses. The coloring matter of cochineal, also, has received 

 attention. Liebermann and Van Dorp have succeeded in re- 

 ducing ruficoccin a coloring matter obtained from carmine 

 by the action of sulphuric acid by the agency of zinc-dust. 

 They thus obtained a crystallized hydrocarbon melting at 

 183 to 188 C, and yielding a quinone on oxidation. Though 

 this hydrocarbon has some resemblance to anthracene, it dif- 

 fers from it in composition and properties. As soon as it 

 can be identified, the synthesis of the colored derivatives of 



