150 



CHEMISTRY. 



An unnecessary amount of time is often spent 

 on qualitative mineral analysis, while an ac- 

 quaintance with the properties of common and 

 important carbon compounds ought to be ac- 

 quired at an early stage. Quantitative work 

 serious work, in which good methods are used 

 and every effort made to secure accuracy 

 might with advantage be taken up much sooner 

 than usual. One of the best means of preparing 

 for original research is to select suitable mem- 

 oirs, and to work conscientiously through the 

 preparations and analyses described. " When 

 chemistry is taught, not with professional or 

 technical objects in view, but for the sake of 

 educational effects, as an ingredient in a liberal 

 education, the primary object is to make the 

 student observe and think. But with young 

 students it is very important to proceed slow- 

 ly, for chemistry is really a very difficult sub- 

 ject at first." 



Concerning the constitution of meteorites, 

 Prof. Lockyer names fourteen elements which 

 occur most constantly in such bodies, and eleven 

 others which occur less frequently or in smaller 

 quantities. Of them, only hydrogen, nitrogen, 

 and carbon occur in an elementary condition. 

 Hydrogen and nitrogen are asserted to be 

 occluded as gases by the stones. Carbon exists 

 in the forms of graphite and the diamond. The 

 proportion of compound substauces known on 

 the earth that are found on meteorites is smaller, 

 many terrestrially common ones being absent. 

 Thus, free quartz has not been found in any 

 meteors. Many of the meteoric chemical com- 

 binations, on the other hand, are unknown to 

 terrestrial mineralogy. A compound of car- 

 bon with hydrogen and oxygen exists as a 

 white or yellowish crystallizable matter, solu- 

 ble in ether and partly so in alcohol, and 

 exhibiting the characters and the composi- 

 tion of one or more hydrocarbonaceous bodies 

 with high-melting points. Various alloys of 

 nickel and iron occur, with which magne- 

 sium is always associated, the four principal 

 of which have respectively six, ten, fourteen, 

 and sixteen equivalents of iron to one of 

 nickel. Among other minerals are Lawrencite, 

 protochloride of iron ; Maskelynite, with the 

 composition of labradorite; and silica (as as- 

 manite). Among the compounds identical in 

 composition and crystallographic character 

 with minerals found on our globe, are magnetic 

 pyrites, magnetite, chromite, and the following 

 silicates : olivine varieties, enstatite and bronz- 

 ite, diopside and atigite, anorthite and labra- 

 dorite, and breunerite. The oxides of carbon 

 have been detected in many meteorites, where 

 they are assumed to have been occluded. When 

 the meteoric substance is heated and examined 

 with the spectroscope, the most volatile ele- 

 ments appear first, and so on in regular order, 

 and this without regard to the proportions in 

 which they are respectively present. 



The blackening of silver chloride under ex- 

 posure to light has been accounted for in 

 various ways. Some chemists attribute it to a 



reduction of the chloride to metallic silver, 

 while others believe that a subchloride is 

 formed. Experiments by Spencer B. New- 

 berry support the former view. The salt was 

 exposed under water with frequent stirring to 

 expose fresh surfaces to the light, and constant 

 circulation of air resulted in each case under 

 two distinct processes of separation in the 

 production of metallic silver. 



The- differentiation of yeast is presented by 

 Mr. C. G. Matthews, of Btirton-on-Treut, as an 

 exceedingly interesting field for experiment, in 

 which may be found some of the causes of 

 yeast deterioration. There are many species 

 of saccharomyces, and of so nearly equal vital- 

 ity, that a variety of ferments are often pres- 

 ent in what the brewer may regard as a pure 

 yeast. Variations in the character of a fer- 

 mentable liquid tending to the nourishment of 

 certain ferments, rather than others, may de- 

 termine the growth of a majority of one spe- 

 cies, especially in the case of spontaneous fer- 

 mentations. A natural selection has doubtless 

 taken place in the case of brewer's yeast, 

 which may be regarded as an educated and 

 modified form from spontaneous or air-sowed 

 fermentation ; and all ordinary yeasts contain 

 a preponderating quantity of this selected 

 form. It is not until an abnormal percentage 

 of some other kind appears that its presence is 

 demonstrable, though some time before this 

 the yeast may have exhibited peculiarities in 

 its action. Hay duck has traced a connection 

 between the amount of nitrogen yeast contains 

 and its fermentative capacity, and has found 

 that an increased nitrogen percentage is ac- 

 companied, as a rule, by increased fermenta- 

 tive power ; but that after a certain limit, the 

 latter diminishes. Yeast takes up nitrogen in 

 proportion to the amount of that constituent 

 existing in the wort, and will take up more at 

 a higher than at a lower temperature. If 

 quick yeast be carried through consecutive 

 worts of high gravity, a marked deterioration 

 ensues owing, doubtless, to a repleted state 

 of the ferment. It has become so rich in 

 protoplasmic constituents that saccharine solu- 

 tions no longer exert their normal stimulating 

 effect, and it is quite possible that in addition 

 the cells are alcoholized or partially asphyxi- 

 ated. Such deteriorated yeast may be restored 

 to activity by fermentation in a comparatively 

 weak wort, and it is a fair reasoning that the 

 surplus constituents are passed into new cells 

 without drawing entirely on the cell-forming 

 constituents of the wort. The visible deteri- 

 oration of yeast by the accession of bacteria is 

 a matter of high importance. All through the 

 process air-borne germs are being conveyed 

 into the products, and when the opportunity 

 arrives they take effect, and this opportunity 

 occurs when the vitality of the yeast has been 

 lowered ; for a healthy fermentation precludes 

 their development. Bacteria then may be rea- 

 sonably regarded as both cause and effect in 

 yeast degeneration. 



