10S 



CHEMISTRY. (CHEMICAL ANALYSIS.) 



tinned i>v the preparation by MM. C. Chabiie and 

 K. Kcngarde of well-characterized alums with 

 ivMiaii and rubidium. 



Announcement \va> made at the annual meet- 

 ing of the Chemical Society in London, March 28, 

 that a committee of the society had decided to 

 recommend, in reference to a uniform system of 

 atomic weights, (1) that O=KJ be taken as the 

 basis of calculation: and (2) that in assigning a 

 number as the atomic weight of any element, only 

 so many figures should be employed that the last 

 may be* regarded as accurately known to one unit 

 in that figure. 



A method of estimating sulfids, sulfydrates, 

 polvMillids. and hyposulh'tes coexisting in so- 

 lution, particularly in certain mineral waters, 

 described by M. Armand Gautier, is based upon 

 the fact that sulfydrates, distilled in a vacuum, 

 give up all their sulfuretted hydrogen in excess 

 of that required to form the monosulfid, and this, 

 again, yields the whole of its sulfur on distilling 

 in a current of carbon dioxid. 



Chemical Analysis. All ordinary sulfuric 

 acid contains silenium or oxidized compounds of 

 it, and such compounds can generally be detected 

 in the purer acid supplied to laboratories for 

 pharmaceutical purposes. Two fairly sensitive 

 methods of detecting selenium are described. One 

 is by the use of codein, which gives an intensely 

 blue coloration to the sulfuric solution of sele- 

 nious acid; and the other is by the precipitation 

 of selenium when sulfurous acid is passed 

 through sulfuric acid diluted with four times its 

 volume of water. M. Ad. Jouve regards the sele- 

 nium as existing in the sulfuric acid in the forms 

 of selenious and selenic acids. He records experi- 

 ments in the examination for selenium in raw 

 acetylene passed over sulfuric acid, and adds 

 that the detection of selenium in sulfuric acid 

 is of some interest if the acid is to be used in the 

 free state, whether from the pharmaceutical point 

 of view or under other circumstances in which it 

 might be introduced in small quantities for sele- 

 nium compounds are far from being harmless to 

 the human organization. 



A very close chemical relationship has been ob- 

 served by Nencki and Marchlewski between the 

 red coloring matter of the blood and the green 

 chlorophyl of plants. Hematoporphyrin, a de- 

 rivative of hemoglobin, and phyllocyanin, ob- 

 tained from chlorophyl, both yield on reduction 

 hemopyrrol, which is probably an isobutyl or 

 methyl propyl pyrrol. 



Water containing the most minute traces of 

 lead affords to the naked eye a faint though per- 

 sistent opalescence, a fact which has given rise 

 to the opinion that the toxic metal is in com- 

 bination with some organic matters. Of such char- 

 acter are waters that have remained for a long 

 time in new pipes or in old pipes which have 

 been disturbed by some repairs or soldering. 

 Waters exposed when in contact with lead to the 

 silieious and Carbonated dust of the air are always 

 contaminated with nitrated particles. For the 

 detection of lead. M. Hillocq uses a zinc reagent 

 in which the soda has been replaced by ammonia. 

 This reagent is added in excess to the suspected 

 water, and left quiet for several hours. The abso- 

 lutely limpid supernatant water is then decanted 

 off, and the rest is thrown on a filter. The filtra- 

 tion is very rapid, and the dried precipitate is 

 easily detected. This is decomposed with warm 

 acetic acid containing a little acetate of ammonia, 

 and is filtered. The clear acid filtrate is touched 

 with a small glass rod wetted with a solution of 

 chronmte of potassium. Jf the water contains 

 lead, a yellow cloudiness appears, and after the 



lapse of some time a precipitate of chromate of 

 lead is formed. Absolutely limpid water gives no 

 trace of lead with this reaction. 



In the ordinary analysis of feeding stuffs, it has 

 been the general custom to determine only a few 

 of the many constituents present; for the compu- 

 tation of ratios or for the determination of feed- 

 ing values; an estimation of the moisture, fat, pro- 

 tein, ash, and fiber is all that is usually required, 

 the percentage of undetermined matter being sim- 

 ply designated " nitrogen-free extract." This 

 method of procedure, though sufficient for many 

 purposes, is not scientifically accurate, and chem- 

 ists have for a long time felt that a closer study 

 should be made of the various substances or 

 groups of substances, such as ether extract, pro- 

 tein, and fiber, and that more attention should 

 be given to the bodies making up the nitrogen- 

 free extract. Considerable work has been accom- 

 plished in such analysis during a few years past. 

 Good workable methods have been adopted for 

 the determination of sugars, starch, and pento- 

 sans, and some attempts have been made toward 

 a separation of the various lignine and cellulose 

 bodies that make up the greater part of what is 

 termed crude fiber. In many cases, more particu- 

 larly in the analysis of grains, the percentages of 

 the various constituents will approximate very 

 closely 100 per cent.; but in other cases, with 

 feeds rich in fiber, a considerable discrepancy still 

 exists. Messrs. C. A. Browne, Jr., and C. P. Bris- 

 tle describe an analysis they have made on the 

 principles indicated (Pennsylvania State College 

 Agricultural Experiment Station) of a sample of 

 distillery w r aste. In conclusion, the authors re- 

 mark that while the sum of the percentages of the 

 different constituents in many feeding stuff's does 

 not equal exactly 100 per cent., the results are as 

 close as can be expected with the present methods 

 of analysis. 



Acetylene gas has been found by Jouve to fur- 

 nish a very delicate test for selenium in sulfuric 

 acid by precipitating it in the elementary condi- 

 tion. 



Experiments in the synthesis of some aromatic 

 aldoxims by means of fulminating silver are 

 described by R. Schall and E. Retsch. If a poly- 

 hydroxylic derivative of benzene is dissolved in 

 ether, some fulminating silver suspended in the 

 solution, and hydrochloric acid led slowly into 

 the well-cooled solution, the silver fulminate dis- 

 appears and the hydrochlorid of the new aldo- 

 xim crystallizes out. The method has been suc- 

 cessfully applied to resorcinol, orcinol, pyrogallol, 

 and phloroglucosinol. 



The use of metallic sodium as a reducing agent 

 in blowpipe analysis is recommended by Charles 

 Lathrop Parsons, who finds, contrary to Hempel's 

 experience in that particular, that the reaction 

 takes place with the greatest ease on charcoal. A 

 small piece of metallic sodium is hammered out 

 flat. The substance to be reduced is powdered arid 

 spread upon it, pressed into the metal, with the 

 hammer, and the whole is turned and kneaded 

 into a little ball with a knife blade. It is then 

 placed upon a slight depression in a piece of char- 

 coal and ignited. A momentary flash ensues, and 

 the reduction is accomplished. The residue is 

 then heated before the blowpipe, and as the sodi- 

 um oxid and hydroxid immediately sink into 

 the charcoal, any fusible metallic particles collect 

 easily into a button, and may be recognized in the 

 usual manner. Volatile metals, like zinc, oxidize 

 and yield with surprising readiness the character- 

 istic coatings, and on digging up a little of the 

 charcoal, moistening with water, and placing upon 

 a silver coin, the " Hepar " reaction is obtained if 



