I094
NITROGEN I S FERTILIZERS.
molybdate solution to prevent the precipitation of iron and t h e separation of molybdic acid. T h e successful use of t h e molybdate method in these cases seems to warrant the conclusion that we are needlessly alarmed at the presence of, at least, some forms of organic matter i n phosphate solutions. T h e direct determination of the arailable phosphoric acid possesses several advantages. Only one determination is required instead of two a s by t h e present method. T h e probable error is reduced one-half. W e can also determine the soluble, reverted, insoluble, and total phosphoric acid i n one sample and with one weighing where it now takes two samples and two weighings. T h e saving of time effected by this method is of considerable importance in control and in factory laboratories. whether we use the citrate or the molybdate method, and it is hoped that t h e subject 11-ill receive further attention. I,ABOKATORY OF T H E L T A K S L A S D A G I l l C L ' I T V U A L COI.LF.GE,
cOI.I.EGE P A R K . M A R Y L A N D .
NOTE UPON T H E DETERMINATION OF NITROGEN IN FERTILIZERS CONTAINING NITRATES. ET F. P.YEITCH. R e l e i r e d Septen,ber
J
j,
~899.
O H N F I E L D S ' describes a modification of the Gunning method'. I n this modification potassium sulphide alone is used
in the place of potassium sulphate and sodium thiosulphate. I n Fields' hands the average difference between the methods is 0 . 0 2 per cent.. the niodification giving the higher average. T h e writer has used this modification, carried out in a slightly different manner, with very satisfactory results. T o the nitrate in the digesting flask are added thirty-five to forty cc. sulphuric acid containing thirty-four grams salicylic acid per liter. Allow to stand in the cold until the nitrate is dissolved. Add six or seven grams of finely broken potassium sulphide, heat over a low flame for fifteen minutes, then over the full flame until clear. Cool and distil as usual. T h e following are all the results I have obtained by this niethod. 1
2
T h i s Journal, 18, 1102. r.S. Department of Agricullurc, Divisiou of Chemistry, Bulletin 46.
109.5
TESTING SOILS FOR USING FERTILIZERS. No.
608 648 659 7x9 722 723 725 727 731 733 738 742 747 755 756 757
Gunning. Per cent.
Modification. Per cent.
No.
3.84
767
2.69
2.68
782 786 793 808 809 819 820 833 888 917
2.64 1.24 2.34 1.98
2.59 I. 18 2.39
1.11
1.07 2.13
2.90 6.62
4.45 2.90 1.52 3.09 1.81 2.81 2.52 2.25 3.00 6.50
919
2.15
2.17
3.12 1.96 2.88
4.42 3.22 2.05 2.97
924 927 928 933 941
3.58 1.91 2.61 3.34 2.90
3.58 1.84 2.58 3.26 3.04
{;:; 4.45 2.73 1.48 3.15 1.77 2.73 2.51 2.25
i 4.30 ::z {$Z
Gunning. Modification Per cent. Per cent
2.05
2.18 2.27 2.76 4.26 3.07
Average di fference
2.32
2.83 4.18 3.19
4
0.017.
T h e greatest difference between the methods is 0.17 per cent. and the average difference is 0.017 per cent. It is advisable to use a little more sulphuric acid in the digestion than is used in t h e Gunning method. There was no trouble with foaming, turning up the lamps being the only attention required. Time of digestion was about one and a half hours, being about a quarter of an hour longer than in the Gunning method. The modification seems to give as good results, requires fewer chemicals and less attention than the Gunning method, but requires a little longer digestion. (CONTRIBUTION FROM THE
LABORATORY
OHIO STATE
O F AGRICULTURALCHEMISTRY, UNIVERSITY.]
NOTES ON TESTING SOII,S FOR APPLICATION OF COMMERCIAL FERTILIZERS.’ BY H. A. WEBER. Received September 1 8 . ,899.
F
OR more than twelve years of active service in connection with farmers’ institutes, the writer endeavored to impress upon the farmers the necessity of a more rational method in the 1 Read before the meeting of the American sssociation for t h e Advancement of Science, August 26, 1899.
