ATMOSPHERIC-NITROGEN FERTILIZERS. 6 
phos. Sodium nitrate and ammonium sulphate, the present 
standard inorganic-nitrogen fertilizer materials, were used as ref- 
erence substances. In connection with the experiments on cy ana- 
mid a few tests were made with calcium nitrate alone and in admix- 
ture with cyanamid and also tests on calcined phosphate and basic 
slag as sources of phosphorus. 
The composition of the fertilizer materials used, although varying 
slightly from year to year, is quite accurately expressed in Table h 
Some of the more important features of these materials which have 
a bearing on their utility as fertilizers, particularly from the stand- 
point of production, are briefly discussed in the following pages. 
Table 1. — Composition of fertilizers used. 
Fertilizer. 
Composition (per cent). 
NH 3 . P 2 O 
K 2 0. 
Cyanamid (hydrated and oiled) 
Ammonium nitrate (grained) 
Ammonium chlorid 
Ammonium sulphate 
Ammonium phosphate (mainly NH 4 H2 PO4) 
Ammoniated superphosphate 
Urea. 
Urephos 
Calcium nitrate (grained and coated) 
Sodium nitrate 
Double salt (2NH 4 N0 3 . (NH 4 ) 2 S0 4 ) . . . 
Mixed salt (from NH 4 N0 3 and KC1) 
Mixed salt (from 2NH 4 N0 3 and K 2 S0 4 ). 
Calcined phosphate, sample No. 1 
Calcined phosphate, sample No. 2 
Basic slag 
Acid phosphate 
Potassium sulphate 
22.5 
41.2 
31.0 
25.3 
13.9 
5.4 
55.5 
7.0 
14.9 
18.6 
32.5 
16.5 
19.0 
47.0 
!13.5 
2 4.45 
»27.0 
«11.7 
U6.0 
16.0 
30.2 
25.0 
50.0 
1 Solubility in 2 per cent citric acid instead of standard ammonium citrate solution. 
2 Total P 2 O5 8.1 per cent. 3 Total P 2 5 31.0 per cent. * Total Pj 5 28.7 per cent. 
Cyanamid is a very important form of fixed nitrogen and is man- 
ufactured in large quantities, the estimated capacity of the Muscle 
Shoals plant, for example, being 245,000 tons per annum. Since it is 
the direct product of the cyanamid process of nitrogen fixation, it 
represents a cheaper form 01 nitrogen than any of its transformation 
products, such as ammonium salts, and hence it is important to de- 
termine its fertilizing value. Owing to its chemical nature it can not 
safely be used in large quantities in mixed fertilizers containing acid 
phosphate, and therefore some of the experiments were made using 
mixtures of it with calcined phosphate and basic slag as well as with 
acid phosphate. Since cyanamid nitrifies rather slowly, tests were 
also made in which readily available nitrogen in the form of calcium 
nitrate was used with it. 
Ammonium nitrate is one of the most important synthetic-nitrogen 
compounds. It can be produced by a number of methods, and 
although a somewhat more expensive form of nitrogen than cyanamid 
its manufacture was so highly developed during the war that it is now 
available in large quantities at a price only slightly above that of 
ammonium sulphate on the basis of contained nitrogen. It has the 
advantage over many fertilizer materials in that it contains both 
ammonia and nitrate nitrogen and does not leave a residue in the 
