FRAGMENTS OF SCIENCE. 



861 



ture of the ideals of the two leading Eng- 

 lish universities as to seem worthy of re- 

 production: "However, Dr. Hill made 

 one statement for which we owe him a 

 sincere gratitude. 'The excellence of the 

 classics,' said he, ' lay chiefly in their 

 complete uselessness.' ... In this simple 

 statement is expressed the true value of 

 our old universities. They should be 

 practically useless. They should not 

 teach you to be a good carpenter or a 

 skillful diplomatist. You can not march 

 out of Oxford or Cambridge into any ca- 

 reer which will return you an immediate 

 and efficient income. . . . The other uni- 

 versities of Europe are prepared to cut 

 you to a certain measure, or to render 

 you technically competent. But our Eng- 

 lish universities have hitherto declined 

 to discharge this humble function, save 

 in rare lapses, from a noble ideal. They at 

 least profess to accomplish a far greater 

 task. There is a strange period dividing 

 the man from the boy, which clamors 

 aloud for intelligent discipline, and this 

 discipline Oxford and Cambridge are 

 anxious to supply. The undergraduate 

 is too young to specialize, and not too 

 old to receive instruction. When his 

 period of training is finished he is asked 

 to assume the heavy burdens of life, to 

 discharge tasks which may be dull, and 

 which are rarely concerned with what 

 were once called the humanities. As he 

 passes through the university he may 

 not have the time nor the wit to become 

 a sound scholar nor a profound mathe- 

 matician. But he may, if he understand 

 his privilege aright, linger for a while in 

 the groves of 'practically useless' knowl- 

 edge. He may learn what literature 

 meant in an age when it was concerned 

 only with the essentials of simplicity; 

 he may read the lessons of history when 

 history was still separate from political 

 intrigue. And though he forgets his 

 Greek grammar, though in middle life 

 he can not construe a page of Virgil, yet 

 he carries away from this irrational in- 

 terlude a vague impression of beauty 

 which no other course of education will 

 ever give him." Even for the schoolmen 

 " a vague impression of beauty," what- 

 ever that may mean, seems rather un- 

 practical as an educational ultima Thule. 



The Purple of Cassius. — There are 

 few substances in the field of inorganic 

 chemistry on which so much speculation 



and actual work has been expended as 

 the so-called purple of Cassius. A re- 

 cent article by Mr. C. L. Reese, in the 

 Chemical News, contains some interest- 

 ing information regarding this curious 

 compound. Up to the present time there 

 have, it seems, been two views held as 

 to its chemical nature — one that it is a 

 mixture of stannic acid and metallic 

 gold; the other, that of Berzelius, that 

 it is substantially a chemical compound 

 of purple gold oxide with the oxides of tin 

 possibly mixed with an excess of stannic 

 acid. It has seemed very likely that the 

 substance is a chemical compound of 

 acid character, and that the solubility in 

 ammonia is due to the formation of a 

 salt, but it has been found that by oxi- 

 dation of stannous chloride and by al- 

 lowing very dilute solutions of stannic 

 chloride to stand, the " hydrogel " of 

 stannic acid separated out, which, on the 

 addition of a few drops of ammonia, 

 liquefied and so became soluble in water, 

 just as the purple of Cassius does. There 

 can therefore be no salt formation here. 

 Some comparatively recent work by 

 Richard Zsigmondy, however, seems to 

 have finally cleared up the chemical na- 

 ture of this curious substance. Its for- 

 mation is explained by assuming that 

 when stannous chloride is added to a 

 sufficiently dilute solution of gold chlo- 

 ride the latter is immediately reduced to 

 metallic gold while stannic chloride is 

 formed. Generally after a few seconds 

 the liquid becomes red, but the purple 

 is not precipitated for several days, un- 

 less it is heated. The gold is not pre- 

 cipitated as a black powder because the 

 stannic chloride formed is immediately 

 liydrolized into hydrochloric acid and 

 the hydrate of stannic acid. The latter 

 prevents the aggregation of the gold par- 

 ticles, and tlie stannic acid remains in 

 solution as a colloid, which on standing 

 gradually changes under the influence 

 of the dilute hydrochloric acid to an in- 

 soluble form, the " hydrogel " of stannic 

 acid. By heating, this change takes 

 place immediately. The properties of the 

 purple of Cassius depend on the proper- 

 ties and character of the stannic acid 

 present, and the great variety in the 

 properties of the stannic acids, the or- 

 tho. the meta, and the colloidal mix- 

 tures of the two explain the many con- 

 ti'adictions in the literature with refer- 

 ence to the properties of the purple of 



