1838] 



FARMERS' REGISTER. 



689 



in a forge mixed with charcoal powder. It is a 

 metal very difficult of fusion, and very combustible: 

 its specific gravity is GS50. The number repre- 

 senting it is 177. 



30, Potassium is the lightest known metal, being 

 only o( specific gravity 850, It liiscs at about ISO*^, 

 and rises in vapour at iieat a little below red- 

 ness. It is a highly combustible substance, takes 

 fire when thrown upon water, burns with great bril- 

 liancy, and the productof its combustion dissolves 

 in the water. The number representing it is 75. 

 It may be made by passing fused caustic vegetable 

 alkali, the pure kali of druggists, through iron 

 turnings strongly ignited in a gun barrel, or by the 

 electrization of potash by a strong Voltaic battery, 



31, Sodium may be made in a similar manner "to 

 potassium; soda, or the mineral alkali, being sub- 

 stituted for the vegetable alkali. It is of specific 

 gravity 940, It is very combustible. When thrown 

 upon water, it swims on its surface, hisses violently, 

 and dissolves, but does not mflanie. The number 

 representing it is 88. 



32, Lithium is a metal procured from a newly- 

 discovered mineral alkali, very similar to sodium in 

 its properties, 



33, Barium has, as yet, been procured only by 

 electrical powers, and in very minute quantities, so 

 that its properties have not been accurately exa- 

 mined. The number representing it appears to be 



Strontium the 34th, Calcium the 35th, Magne- 

 sium the 36th, jiluminum the 37th, Zirconum the 

 38th, Glucinum the 39lh, and Ittrium the 40th of 

 the undecompounded bodies, like barium, have 

 either not been procured absolutely pure, or only in 

 such minute quantities that their properties are litile 

 known; they are formed either by electrical powers, 

 or by the agency of potassium, from the different 

 earths whose names they bear, with the change of 

 the termination in urn ; and the numbers repre- 

 senting them are believed to be 90 strontium, 40 

 calcium, 29 magnesium, 33 aluminum, 70 zirco- 

 num, 39 glucinum, 111 ittrium. 



The remaining simple bodies are metals, most 

 of which, like those just mentioned, can only be 

 procured with very great difficulty ; and the sub- 

 stances in general from which they are procured 

 are very rare in nature. They are Palladium, 

 Rhodium, Osmium, Iridium, Cnlumbium, CTiro- 

 mium, Molybdenum, Cerium, Tellurium, Tung- 

 stenum. Titanium, Uranium: The numbers re- 

 presenting these last bodies have not yet been de- 

 termined with sufficient accuracy to render a re- 

 ference to them of any utility. 



The undecompounded substances unite with 

 each other, and the most remarkable, compounds 

 are formed by the combinations of oxygen and 

 chlorine with inflammable bodies and metals ; and 

 these combinations usually take place with much 

 energy, and are associated with fire. 

 tL Combustion in fact, in common cases, is the 

 process of the solution of a body in oxygen, as 

 happens when sulphur or charcoal is burnt ; or the 

 fixation of oxygen by the combustible body in a 

 solid form which takes place when most metals 

 are burnt, or when phosphorus inflames ; or the 

 production of a fluid from both bodies, as when 

 hydrogen and oxygen unite to form water. 



When considerable quantities of oxygen or of 

 chlorine unite to metals or inflammable bodies, 

 they often produce acids ; thus sulphureous, phos- 



phoric, and boracic acids are formed by a union 

 of considerable quantities of oxygen with sulphur, 

 phosphorus, and boron: and muriatic acid gas is 

 iurmed by the union of chlorine and hydroffcn. 



When saialirr (luanlilies of oxyyeii or chlorine 

 unite with iiillanunablc bodies or metals, they form 

 substances not acid, and more or less soluble in 

 water; and the metallic oxides, the fixed alkalies, 

 and the earths, all bodies connected by analogies, 

 ure produced by the union of metals with oxygen. 



The composition of any compounds, the nature 

 of which is well known, may be easily learned from 

 the numbers representing their elements ; all that 

 is necessary is to know how many proportions 

 enter into union. Thus;;o^assa, or the pure caus- 

 tic vegetable alkali, consists of one proportion of 

 potassium and one of oxygen, and its constitution 

 is consequently 75 potassium, 15 oxygen. 



Carbonic acid is composed of two proportions of 

 o.xygen 30, and one. of carbon 11-4. 



Again, Z/me consists of one proportion of cal- 

 cium and one of oxygen, and it is composed of 40 

 of calcium and 15 of oxygen. And carbonate of 

 lime, or pure chalk, consists of one proportion of 

 carbonic acid 41-4, and one of lime 55. 



Water consists of two proportions of hydrogen 

 2, and one of oxygen 15 ; and when water unites 

 to other bodies in definite proportions, the quantity 

 is 17, or some multiple of 17, i. e. 34 or 51, or 

 68, &c. ' 



Soda, or the mineral alkali, contains two propor- 

 tions of oxygen to one of sodium. 



Jlmmonia, or the volatile alkali, is composed of 

 six proportions of hydrogen and one of azote. 



Amongst tbe earths. Silica, or the earth of 

 flints, probably consists of two proportions of 

 oxygen to one of silicon ; and Magnesia, Stron- 

 tia. Baryta or Barytes, Jllumina, Zircona, Glu- 

 cina, and Ittria, of one proportion of metal and 

 one of oxygen. 



The metallic oxides in general consist of the 

 metals united to fi'oni one to lour proportions of 

 oxygen ; and there are, in some cases, many 

 ditierent oxides of the same metal ; thus there are 

 three oxides of lead ; the yellow oxide, or mas- 

 sicot, contains two proportions of oxygen ; the red 

 oxide, or minium, three; and the puce-coloured 

 oxide four proportions. Again there are two 

 oxides of copper, the black nnd \he orange; the 

 black contains two proportions of oxygen, the 

 orange one. 



For pursuing such experiments on the compo- 

 sition of bodies as are connected with agricultural 

 chemistry, a few only of the undecompounded 

 substances are necessary; and amongst the com- 

 pounded bodies, the common acids, the alkalies, 

 and the earths, are the most essential substances. 

 The elements found in vegetables, as has been 

 stated in the introductory lecture, are very few. 

 Oxygen, hydrogen, and carbon constitute the 

 greatest part of their organized matter. Azote, 

 phosphorus, sulphur, manganesum, iron, silicum, 

 calcium, aluminum, and magnesium, likewise in 

 different arrangements, enter into their compo- 

 sition, or are found in the agents to which they are 

 exposed ; and these twelve undecompounded sub- 

 stances are the elements, the study of which is of 

 the most importance to the agricultural chemist. 



The doctrine of definite combinations, as will 

 be shown in the following lectures, will assist us 

 in gaining just views respecting the composition 



