RECENT WORK IN AGRICULTURAL SCIENCE. 



CHEMISTRY. 



On the losses of sulphur in charring- and in ashing plant substances; and 

 on the accurate determination of sulphur in organic substances, W. E. Bar- 

 low {.lunr. Aiiicr. Chan. Soc, 20 {1904), ^o. 4, jy>- 341--^''>7, f(j.i. S). — This article 

 fiives details of studies of a large number of methoils of inciueratlng organic sub- 

 stances carried out at Gottingen University under direction of Prof. B. Tollens. The 

 general conclusions reached are as follows: 



"(1) In ashing a plant substance, a protein or a coal in the ordinary manner, 

 without addition of alkali, a loss of sulphur always takes place. This loss is always 

 considerable, and may be, in some cases, enormous, even when precautions are taken 

 to insure a low temperature and a slow and regular ashing. It is caused by the con- 

 version of organic suli)hur into volatile sulphur compounds and into sulphur dioxid 

 and trioxid during the charring and ashing. A certain part of these is retained by 

 • the bases, especially by the alkalis, l)ut in presence of phosi)horic and silicic acids, 

 which expel sulphuric acid at a red heat, the amount retained in the ash may be 

 very small or even nothing. 



"(2) The loss takes place even when there is a quantity of alkaline base present 

 more than sufficient to combine all the acid. 



"(3) The loss is diminished (but by no means entirely avoided) by the addition 

 of amounts of sodium carbonate up to twice the weight of the substance to be ashed. 

 The additional effect of adding more sodium carbonate is practically nothing. 



" (4) The loss of sulphur is not entirely prevented either by the addition of calcium 

 acetate before ashing (Tucker) ; or, of magnesium oxid and sodium carbonate together 

 (Eschka); or by evaporation with potassium hydroxid followed l)y oxidation with 

 potassium nitrate; or by evaporation with nitric acid and potassium nitrate before 

 ashing (Fraps). In all these cases the gases still contain sulphur. 



"(5) By far the greater part of the loss of sulphur occurs during the preliminary 

 charring, a much smaller ])art during the burning of the charred mass to ash. 



"(6) Combustion in a stream of oxygen, with absorption of the sulphur-containing 

 products of charring and combustion either in heated sodium carbonate in the com- 

 bustion tul:)e or in a special apparatus, gives, under proper conditions, absolute values 

 for the total sulphur. Such results are, however, exceedingly difficult, if not quite 

 impossible, to attain by either the original Berthelot method or the Sauer method. 

 The writer considers that he has ascertained and described the arrangement of ap[)a- 

 ratus and the details of manipulation which render possible the attainment of such 

 accurate results with ease and certainty. It is essential to burn the escaping gases 

 completely with an excess of oxygen, introduced laterally at a certain point in the 

 combustion tube, before aV)sorbing the sulphuric acid from them." 



Investigations on the accurate determination of sulphur in plant sub- 

 stances and other organic materials, W. E. Barlow (Iikou/. />/.s.s-., Unir. Gotlin- 

 gen, 1903, pp. S7, figs. 3, dgm. 1; abs. by B. Tollens, in Jonr. Landw., 51 {1903), No. 3, 



952 



