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LI. On the Amount of Sulphur and Phosjjhorns in various 

 AgricuUural Crops. By Henry Clifton Sorby, Esq."^ 



HAVING thought it highly probable that in the ordinary 

 method of estimating the amount of sulphur and phos- 

 phorus in plants, viz. by burning them and analysing their 

 ashes, there might be in many cases a loss from portions 

 being rendered volatile by contact with combustible matter 

 at a high temperature, I was induced to commence a series 

 of analyses, employing a method against which there was no 

 such objection, and, as will be seen, the quantities really pre- 

 sent in various plants are much greater than has been hitherto 

 anticipated. Having obtained a proper specimen, one por- 

 tion of known weight was dried at 212° F. and weighed, and 

 another in precisely the same condition was employed for the 

 analysis, the amount which I generally used varying with the 

 di-yness of the substance from 200 grs. to 500 grs., which 

 was cut into pieces if necessary, and inti'oduced into a flask, 

 and carefully heated with pure nitric acid, a little water being 

 added if the substance was a dry one. No large quantity of 

 the acid is required, and a gentle heat is kept up until the 

 whole is digested down into a yellowish pulpy mass ; water 

 is then added, the whole boiled, and when cold filtered and 

 washed, there being invariably a quantity of white fibrous 

 substance left undissolved. To the yellowish solution thus 

 obtained nitrate of baryta was next added, and though at first 

 perhaps no precipitate was formed, sulphate of baryta was 

 gradually deposited, and after standing for a day or so, the 

 precipitate was collected on a filter, washed, dried, ignited and 

 weighed, from which the amount of sulphur was calculated. 

 It is well to ascertain whether it is pure sulphate of baryta, 

 by adding to it after weighing a little hydrochloric acid, since 

 sometimes there was present a little carbonate, which of course 

 produces effei'vescence, and when that is the case, which sel- 

 dom occurred to any but the most trifling extent, the amount 

 is easily ascertained and a proper deduction made, to obtain 

 the true weight of the sulphate alone. 



To the solution filtered as above, I next added acetate of 

 lead in moderate quantity, and then caustic ammonia in slight 

 excess, filtered and washed the precipitate. When dry this 

 precipitate was carefully calcined in a porcelain crucible over 

 a lamp, at as low a temperature as convenient, stirring with 

 a glass rod until the Avhole was converted into a mixture of 

 metallic lead, oxide and phosphate of lead. These were then 

 dissolved in nitric acid, and ammonia added until a consider- 



* Communicated by the Chemical Society; haviiiii been read Dec. 7, 

 1846. 



