CHEMISTRY. 



97 



COLOROMETEIO ESTIMATION OF CARBON IN 



IRON. The great extension which has taken 

 place in the applications of steel has made it 

 desirable to obtain tests for the presence of car- 

 bon of a more minute degree of exactness than 

 has heretofore been deemed sufficient. Profes- 

 sor Eggertz has described, in the " Jern Kon- 

 torets Annalen," a method of colorometric esti- 

 mation which is applicable to cases in which an 

 exactness of 0-01 per cent is wanted. The basis 

 of his process is the solution of ferric hydrate 

 in nitric acid, to which a volume of water equal 

 to that of the acid is added ; when the quan- 

 tity of acid used is commensurate with the 

 proportion of carbon in the iron, the yellow- 

 green color of the solution is cleared on adding 

 an equal volume of water. Care must be taken 

 that no chlorine is present, for the slightest 

 trace of that substance gives a yellowish tint. 

 The quantity of nitric acid required for solu- 

 tion is regulated to a certain degree by the 

 supposed amount of carbon in the iron. For a 

 solution with a lower amount of carbon than 

 0'25 per cent, 2 - 5 c. c. of nitric acid should be 

 nsed for O'l gramme of iron ; with carbon of 0'3 

 per cent, 3 c. c. ; with carbon of 0'5 per cent, 3-5 

 c. c. ; and for carbon of 0-8 per cent, 4 c. c. of 

 acid. When the amount of carbon is altogether 

 unknown, begin with 2*5 c. c. of nitric acid, and 

 afterward add more as soon as the color of the 

 solution or the amount of separated carbon 

 shows that more acid is required. Too little 

 acid gives too deep a shade, while excess of 

 acid may be remedied by adding more water. 

 The iron to be tested should be finely divided 

 by filing, boring, planing, or crushing. The 

 solution should be made at 80 C., with shak- 

 ing of the tube. It is often more convenient 

 to put the tube in boiling water ; and speed 

 can be gained at the expense of having a red- 

 dish-yellow film to deal with, by gently boil- 

 ing the mixture. Special normal solutions, 

 for comparison, are prepared in the same man- 

 ner and graduated by successive dilutions from 

 the normal, which represents O'lO per cent of 

 carbon per c. c. of O'l gramme of iron, and may 

 be used for iron with 0'8 per cent and higher 

 of carbon, down to the ^ normal which rep- 

 resents 0'005 per cent of carbon, and is used 

 for iron with from 0'04 to 0'08 per cent, or the 

 lowest amount of carbon found! The distribu- 

 tion of the light in the room should be consid- 

 ered in applying the test, and it should be ob- 

 served that a tube held on the right is gener- 

 ally a little weaker in color than one held on 

 the left. The presence of manganese in the 

 iron communicates a brown color, which is 

 changed by heating to 100 C. to a weak red- 

 violet; chromium gives a grayish blue; vana- 

 dium, a weak yellow ; nickel, a green all of 

 which colors vanish under a greater or less di- 

 lution with water. Cobalt gives a red color 

 which can not be regarded as absent till 

 the dilution has extended to 40 c. c. Phos- 

 phorus, sulphur, copper, silicon, in the pro- 

 portions in which they were tested by Pro- 

 VOL. xxi. 7 A 



fessor Eggertz, did not perceptibly affect the 

 color. 



A NEW VEGETABLE COLORING PRINCIPLE. 

 Messrs. S. P. Sadtler and W. L. Rowland have 

 analyzed a new vegetable coloring matter 

 found in the West-African wood called beth- 

 a-tarra, a wood which is much valued for its 

 extreme toughness and its capability of receiv- 

 ing a high polish. The wood is compact, very 

 heavy, and of nearly the color of black-walnut. 

 On close examination the interstices of the 

 fibers are seen to be filled with a yellow, crys- 

 talline powder. In this respect the beth-a- 

 barra differs from logwood, barwood, cam- 

 wood, and red sandal-wood, with which it was 

 compared, in which the color is uniformly dis- 

 seminated, and the fiber appears as if it had 

 been soaked in a solution of corresponding 

 color. The solution of the coloring matter 

 obtained by extracting from the sawdust or 

 raspings was treated for precipitation with 

 acetic acid, and the pure substance was ob- 

 tained by successive crystallizations from the 

 alcoholic solution of the precipitate. The ma- 

 terial thus gotten is a tasteless, yellow com- 

 pound, apparently crystallizing in scales and 

 needles, which are found under the microscope 

 to be made up of a series of flat prisms, joined 

 laterally. The crystals are unchanged in dry 

 or moist air, insoluble in cold water, very 

 slightly soluble in hot water, but readily solu- 

 ble in alcohol and ether; they dissolve with a 

 deep claret-red color in the presence of even a 

 trace of alkali or alkaline carbonate, and melt 

 at 135 C. Analysis gives a composition for 

 the material dried at 125 C. which is repre- 

 sented by the formula CasHaaOs, or possibly 

 CaaHasO 4 , and for that dried at 100 C., C 38 

 HasOs + SHaO. The beth-a-barra presents a 

 similarity in many of its reactions leading 

 to the suspicion of a relationship with chryso- 

 phanic acid and chrysarobin. 



ACTION OF SEA-WATER ON CAST- IRON. Pro- 

 fessor A. Liversidge, of the University of Syd- 

 ney, has made a study of the action of sea-water 

 on cast-iron in the case of the screw of the steam- 

 dredge Hunter, which became so rotten that it 

 had to be removed. Even on the most cursory 

 examination the specimen was seen to differ 

 entirely from the original cast-iron, except in 

 its shape, which remained unchanged. The 

 material was so altered in composition that it 

 might be safely described as a pseudomorph, 

 since it was almost entirely made up of oxide 

 of iron and particles of graphite. It was quite 

 sectile, being readily cut with a knife. The 

 powder under the microscope presented a mixt- 

 ure of brilliant scales of graphite with brown- 

 colored oxide of iron and a few widely scattered 

 minute particles of metallic iron. The exter- 

 nal part of the specimen was of a dull-gray 

 color, while within it was rusty brown, with 

 dark bands following more or less closely the 

 outer contour lines. The specific gravity was 

 found to be only 1-63. Phosphorus appeared 

 to have been completely eliminated by the 



