CHEMISTRY. 



Ill 



value for oxygen at 15-96, the atomic weight 

 of gold is fixed by the average result of their 

 analyses at 196*85 ; but if, with Mendelejeff, 

 we consider oxygen 16, the atomic weight ot 

 gold becomes 197 ; 28. Mendelejeff considered 

 the old value of gold, 196-2, to be too low, 

 because there was no place in the periodic sys- 

 tem for an element of that atomic weight hav- 

 ing the properties of gold. Hence the result 

 of the present determination has been to place 

 gold in what seems to be its proper position in 

 the periodic classification. 



Gerhard Krtiss has determined the atomic 

 weight of gold by the analysis of neutral tri- 

 chloride and of potassium gold bromide. The 

 mean value derived from five methods was 

 196-669. The author regards 196-64 as most 

 probably correct. 



A. 0. Cousins has observed, in studying the 

 relations between gold, thallium, and mercury, 

 that the atomic weight of mercury is the mean 

 of those of gold and thallium ; that its specific 

 gravity in the liquid state is very nearly the 

 mean of their atomic volumes ; and that its 

 own atomic volume is almost exactly the theo- 

 retical specific gravity of an alloy formed of 

 equal weights of gold and thallium. 



Prof. Carnelly, in a paper in the British As- 

 sociatj;c"von "The Antiseptic Properties of 

 Metallic Salts in relation to their Chemical 

 Composition," held that there was a relation 

 between the atomic weights of various sub- 

 stances and their antiseptic properties, and 

 suggested that there was a distinct relation be- 

 tween the power which these antiseptic bodies 

 had upon animals and those which they pro- 

 duced upon micro-organisms. 



Prof. Thorpe and Mr. J. W. Young have de- 

 termined the atomic weight of silicon, from the 

 tetra-bromide, which they prepared in consid- 

 erable quantity, at 28'332. 



Apparatus. J. B. Mackintosh has devised an 

 improved form of Elliott's gas-apparatus to ob- 

 viate difficulties in the ordinary form of that 

 apparatus, and prevent the liability of acci- 

 dentally introducing some air during the oper- 

 ation. The essential feature of the apparatus 

 is a three-way T-stopcock on the measuring 

 burette, by which connection may be made be- 

 tween any two of the burettes to the complete 

 isolation of the other. Another time-saving 

 device is in the fixing of the zero-points of the 

 graduations. In the measuring and explosion 

 burettes the zero-point is taken at that point 

 where the capillary-tube expands into the bu- 

 rette, and where the water will naturally re- 

 main when the excess drains to the bottom of 

 the burette. This renders the adjustment to 

 zero an automatic one, with no sacrifice of 

 accuracy. The absorption-tube has a single 

 gradation at lOOcc. 



A new form of spectroscope has been devised 

 by G. Kriiss, which is based upon the Bunsen 

 and Kirchhoff instrument, but has received a 

 number of modifications and additions adapted 

 to make it available as a universal spectroscope. 



With it, spectrum measurements may be made 

 between two colors whose wave-lengths differ 

 by only 0.000,000,000,015mm. The inventor 

 thinks that the results obtained by this instru- 

 ment when used as a spectro-photometer, are 

 fully equal, if not superior, to those obtainable 

 with polarizing instruments. 



Charles W. Folkard has described a simple 

 apparatus, made from ordinary laboratory ap- 

 pliances, for the bacteriological examination of 

 water. Test-tubes, about 7 inches long and 

 seven-eighths of an inch in diameter, are used 

 to receive the nutrient jelly. They are closed 

 by a plug of cotton-wool, which is tied by 

 thread round a piece of glass tube bent at right 

 angles and drawn off at one end. The bent 

 tube has a capacity of Ice., and serves for the 

 introduction of the measured quantity of water 

 for experiment. The whole is sterilized in the 

 usual way. The water, of which a sample is to 

 be examined, is allowed to run through a piece 

 of three-eighths-inch India-rubber tube (pierced 

 with a small hole in the middle, and furnished 

 with a glass jet at the end) till all the germs 

 on the tube have been washed away. The cap- 

 illary end is passed through the hole in the 

 India-rubber tube, and sufficient time is al- 

 lowed for any germs on it to be washed off. 

 The capillary end is then broken off by the 

 fingers or by a pair of pliers, while it is inside 

 the India-rubber tube. The water (which is of 

 course running all the time) fills the bent tube, 

 being assisted, if necessary, by partially stop- 

 ping the glass jet for an instant. The bent 

 tube is then withdrawn, the capillary end is 

 sealed in the flame, and the Ice. of water is 

 transferred to the test-tube by shaking. 



Schall has constructed a balance on which 

 the ratio of the density of any given gas to that 

 of hydrogen and hence the molecular weight 

 of this gas may be read directly from the de- 

 flection. 



Agricultural Chemistry. Sir J. Lawes and Dr. 

 Gilbert, reporting in the British Association on 

 "The Present State of the Question of the 

 Sources of Nitrogen in Vegetation," quoted the 

 opinions of a number of writers on the culti- 

 vation of the soil, and said that the results at 

 present are extremely conflicting as to whether 

 free nitrogen comes into play in any way. The 

 results quantitatively are most discrepant, and 

 the explanations are almost as numerous as the 

 observers ; still there are many results which 

 can only be explained in one of two ways: 

 either error was at work or free nitrogen was 

 brought into operation. The authors thought, 

 however, that they must hold their opinions in 

 abeyance for the present. They dwelt upon the 

 experiments which had been made in the rais- 

 ing of various crops, and said it was shown that 

 nitrogen was derived from the residue of crops 

 previously taken from the soil. There was 

 clear evidence of nitrification of the subsoil in 

 certain cases. The evidence was at present in- 

 adequate to justify a definite conclusion upon 

 the matter. 



