CHEMISTRY. 



85 



the treatment his ooilcrs have re- 

 <vi\ed during the voyage by cxiiinination and 

 anaksisof the scale in them. With the intro- 

 duction of high- pressure steam, a new and very 

 dangerous form of deposit has appeared in boil- 

 er^. It is derived from the oil that distills into 

 the boiler from the lubricants used in the cylin- 

 der, the formation of which on the plates per- 

 mits them to pet superheated and in a condition 

 to collapse. Experiments and analyses are re- 

 corded in the author's paper showing how this 

 distillation takes place, even in mineral oils, 

 when in contact with steam, at temperatures con- 

 siderably below their estimated boiling points. 

 The distilled oil forms a scum on the top of the 

 water, which remains there until the particles 

 of lime salts present, coming in contact in the 

 course of the circulation with the greasy par- 

 ticles, gradually acquire the gravity of the water, 

 and then, going along with the convection cur- 

 rents, stick to any surface with which they come 

 in contact. Such a deposit is more likely to be 

 produced with boilers containing fresh or dis- 

 tilled water. The great points to be sought in 

 a good lubricating oil are that it shall be a pure 

 mineral oil, and that its boiling point shall be 

 well above any temperature likely to be attained 

 in tin- cylinder. For the prevention of the oily 

 deposits, the author recommends, therefore, fil- 

 tration of the condenser water through a coke 

 column for the removal of traces of oil, free use 

 of the scum cocks, the use of water of consider- 

 able density rather than of fresh water, and the 

 use of pure mineral-oil lubricants in the smallest 

 possible quantity. 



Chemical Synthesis. A new and simple 

 method of synthesizing tartaric acid i? described 

 by M. Genvresse. It is by the action of nascent 

 hydrogen on glycoxylic acid. A mixture of 

 glycoxylic and acetic acids is treated in small 

 quantities at a time with zinc dust. After re- 

 moval of the zinc and treatment with calcium- 

 chloride solution, a white crystalline precipitate 

 separates, which yields all the reactions of a tar- 

 trate and proves to be tartrate of lime. The 

 tartaric acid obtained by this synthesis is the 

 optically inactive variety known as racemicacid. 



The synthesis of the minerals crocoite and 

 phoenicochroite may be accomplished, according 

 to C. Ludeking, by exposing for several months 

 to the air a solution 01 lead chrornate in caustic 

 potash, in a flat dish or plate. It is possible 

 thus to obtain a mixture of the crystals of the 

 two, from which individual crystals may be 

 easily picked out. The author 'also obtained 

 each of the minerals alone. By using a large 

 excess of very strong solution of potash, phcenico- 

 croite was formed, with only a very little croco- 

 ite : when, on the contrary, much PbCrOi was dis- 

 solved, and in addition K a Cr0 4 was added to the 

 potash solution, crocoite alone was formed. The 

 I't>('rO 4 crystals are oblique rhombic prisms 

 with many modifications. The fracture is un- 

 certain, luster adamantine, color hyacinth-red. 

 They are stable in the air. The phoenicochroite 

 cr\ -tals are tabular, of resinous luster, of cochi- 

 neal color, and appear to be orthorhombic. They, 

 like the natural crystals, have little stability, 

 and soon change, on exposure, to a light-yellow 

 powder. 

 In a paper at the British Association, Prof. 



On in Hrown showed how, by an extension of 

 the electrolytic methods which had been already 

 fully worked out in relation to potassium ace- 

 tate, the higher fatty acids of other series could 

 be synthesized. Thus, starting from the ethyl 

 potassium malonate, the ether of succinic acid 

 was obtained in considerable quantity and with 

 great readiness. Similarly adipic. sebacic, and 

 other ethers had been obtained. Secondary prod- 

 ucts were formed which in the higher members 

 of the series accumulated in inconveniently 

 large quantities. 



A synthesis of troilite, the crystallized mono- 

 sulphide of iron. FeS, which is frequently found 

 in meteorites and never in terrestrial rocks, has 

 been effected by Richard Lorenz, of Gottingen. 

 The crystals were obtained when a stream of 

 dry sulphureted hydrogen gas was led over a 

 bundle of iron wire contained in a combustion 

 tube heated in a furnace. At a dull-red heat 

 the wire became covered with brilliant little 

 crystals that presented a bright, silver-white 

 luster when first obtained, but after a time re- 

 flected a pale-green light. After some days they 

 further changed to blue, and then to brown, 

 without changing form. Wurtzite, sulphide of 

 zinc, ZnS, may be readily artificially obtained in 

 a similar manner by passing sulphureted hydro- 

 gen over zinc heated to whiteness. 



The syntheses of azoamide (NH) hitherto ef- 

 fected, nave all depended upon the introduction 

 of an organic substance at some stage of the 



Erocese. Prof. Wislicenus has now obtained it 

 y means of a simple reaction involving only 

 inorganic substances, or by the interaction of 

 ammonia gas and nitrous oxide in the presence 

 of heated metallic sodium. 



Agricultural Chemistry. From a special 

 study of the process of the passage of granite 

 rock into fertile soil, Alexander Johnstone finds 

 that the agents concerned in the work are me- 

 chanical, chemical, and vital. The mechanical 

 agencies produce the largest results in bulk, and 

 the principal of them is frost. The first chem- 

 ical change coming over the rock is the peroxi- 

 dation of some of the iron that is always present 

 in its mass, which increases to the greatest ex- 

 tent where air and water can most readily enter. 

 The surface of the rock becomes browned with 

 the hydrated ferric oxide formed, and brown 

 skins, of a deeper color than the surface gener- 

 ally, coat the walls of the original rock joints. 

 There are in the mass of the rock, awav from 

 these primary fissures, areas more permeable than 

 others from the surf ace, and through these streaks 

 of ferric oxide are produced. These lines of rust 

 are the beginnings of a new set of joints, which 

 the author calls weather joints, to distinguish 

 them from the primary joints of consolidation 

 and rock movements. Very soon the work of 

 carbonation is seen to be progressing along with 

 the oxidation of the iron, but at a slower rate. 

 The carbonic-acid gas of moist air. dissolved in 

 the penetrating water, attacks the feldspars, the 

 biotite, and the hornblende. Two processes of 

 decomposition have been noticed that which 

 occurs when the carbonic acid is in excess or can 

 obtain free access to the mineral, and that which 

 takes place when either of the opposite condi- 

 tions prevails. In the first case, the feldspar, sup- 

 posing it to be orthoclase, has the molecules of 



