SULPHOCYANATE OF SALIVA. 345 
pathological conditions, but are not normal constituents. Grape-sugar 
and bile pigments are never found even in the Beveresl cases of diabetes 
or icterus. 1 
Inorganic constituents. — These consist of salts of the alkalies (chiefly 
sodium) and alkaline earths ; principally as chlorides, but also as 
phosphates and carbonates. 2 Calcium carbonate often separates from 
saliva, as a thin surface film, or as a cloudiness in the fluid on standing; 
this is due to the escape of carbon-dioxide by which the calcium was 
held in solution as bicarbonate. A precipitation of the calcium of the 
saliva, partially as carbonate and partially as phosphate, in the ducts of 
the salivary glands, often gives rise to salivary concretions; and a similar 
deposit, mixed with phosphate and traces of silica, forms the tartar 
of teeth. 
SulpTwcyanate of saliva. — Treviranus, 3 as early as 1814, observed 
that when a dilute solution of ferric chloride is added to saliva a reddish 
coloration is obtained. This was even before sulphoeyanic acid was 
known chemically, and Tiedemann ami Gmelin 4 afterwards proved that 
the effect was due to the presence of a sulphocyanate. 
The amount of sulphocyanate is not large. Oehl states it as equivalent to 
0-00016-0-0084 per cent., estimated as potassium sulphocyanate, and Munk 
as equivalent to 0"01 per cent, sulphoeyanic acid, or - 014 per cent, of 
sodium sulphocyanate. 5 The presence of a sulphocyanate in saliva may be 
demonstrated qualitatively in several ways — (1) A very greatly diluted and 
slightly acidulated solution of ferric chloride is added drop by drop to saliva, 
when a reddish coloration is obtained, if sulphocyanate is present in normal 
quantity ; the colour disappears on adding mercuric chloride. This test is 
difficult to obtain. (2) A filter paper is dipped in a weak solution of ferric 
chloride, containing a trace of hydrochloric acid, and then allowed to dry, when 
it should have only a faint amber colour. On such test paper a drop of saliva 
produces a reddish stain. (3) Filter paper is impregnated with tincture of 
guaiacum, and then drawn through a solution of - 05 per cent, copper sulphate. 
On such paper, saliva containing sulphocyanate causes a blue stain. 1 (4) Saliva 
is treated Avith iodic acid, when iodine is set free ; this in turn is treated with 
starch paste, when the blue compound of starch and iodine appears. This is 
said to be an exceedingly delicate reaction, showing a most minute trace of 
sulphocyanate, and not being produced by saliva free from sulphocyanate, 8 but 
iodic acid is an exceedingly unstable compound, and the latter statement is 
questionable. 
Sulphocyanate is often absent in human saliva. Some authors state that 
it is found in dog's saliva, others that it is not ; the explanation ma) r be that 
its presence in dog's saliva is also not constant. It is said to be absent hi the 
saliva of the horse, ox, sheep, goat, and pig. 9 Leared 10 found that sulpho- 
1 See Maly, Hermann's "Handbuch," Bd. v. (2), S. 8. • 
2 The older analysts were accustomed to proportion the bases and acids, on the 
supposition that as much as possible of the so-called strongest acid was combined with the 
strongest base. We now know that the acids and bases are distributed according to definite 
laws, and no longer speak of so much chloride, for example, as existing in a complex 
mixture, but state separately so much sodium and so much chloriue, etc. 
3 " Biologie," 1814, Bd. iv. S. 330. 
4 " Die Verdauung nach Versuehen," Bd. i. S. 8. 
5 See Maly, Hermann's "Handbuch," Bd. v. (2). S. 10, 14. 
6 Gscheidlen, Jahresb. it. d. Fortschr. d. Thier-C'hem., Wiesbaden. 1874, Bd. iv. S. 91. 
7 Bettger, ibid., 1872, Bd. ii. S. 204. 
8 Solera, ibid., 1877, Bd. vii. S. 256 ; 1878, Bd. viii. S. 235. 
9 Ellenberger and Hofmeister, " Vergleich. Phys. d. Haustiere," Berlin, 1390, S. 
495. 
10 Proc. Roy. Soc. London, 1S70, vol. xviii. p. 16. 
