OR'GANOG'RAPHY (from (;k.. or gonon, organ graphia, writing. from to write). That of biology which treats of the origin and cause of form. LEAF : STEM: ROOT. ORGANO-METALLIC COMPOUNDS. An interesting group of chemical compounds. in maranie Tadieles, such as methyl. Cl . ethyl. (' II . etc.. are united to metals. Zinc-ethyl. (Odell is a !rood example of the class, is obtained by di gr:111111ali•el zinc With et hyl led l J. at a temperature of about 266 F.. for several hours. It is thus obtained in the form of a colorless, transparent, mobile li aid, stiongly refracts light, has a powerful, rather disagreeable odor, and is considerably heavier than water. boiling-poim is l Is t .244.4 1'.1. Chemically, it i, very unstable, and w hen exposed to the air it takes fire spout:imam-1y; it must, therefore, he handled with care and kept in vessel: tilled with carbonic avid gas. The properties of the other I 1 rgii no-metallic com pound, of zinc. stall as zinc-methyl, CI 1,1. zinc-propyl. etc.. are similar to those of zinc•t•thyl, and are the Ilicthod. of preparing them. Among the eorresponding com pounds of lead must be mentioned lead tetra-ethyl. Pb I Cd1,1 „ and lead tri-ethyl. which probably corresponds to the molecular formula The former of these may be obtained by the ac tion of lead chloride on zinc-ethyl. the latter by the action of an alloy of I part of sodium and 3 part, of lead on ethyl iodide. It will be seen
that while in its most stable inorganic com pound, lead is divalent, in its organic compounds it is quadrivalent : in the case of its tetra-ethyl compound this is evident ; lint the tri-ethyl, too, probably has t he eonst it ution — Ph( and hence contains lead in the quadri valent state. other metal, capable of forming organic include mercury, magnesium, cadmium. aluminum. thallium, and probably also sodium and potassium. In the ease of metals whose at0111, pusses: more than unit valency. min pounds have been obtained in whine molecules a metallic atom is combined at the same time with organic radicles and with halogen atoms hike chlorine or iodine) or hydroxyl groups (011). Thus the compound known as mercury-ethyl chloride has the formula Cd1,1 !gel. mercury methyl iodide has the formula lead-tri methyl hydroxide has the formula Phi CI I,).,01], etc. The hydroxyl-compounds, like that just mentioned, are strongly basic—about as strong, in fact, as caustic soda or caustic potash.
The organo-metallie eompound, are useful in the synthetic preparation of a number of organic substances. They were discovered by Frankland, and it was while studying these compounds that Frankland first conceived the idea of valency, which formed the most important part of the atomic theory.