66 , REPORT—1874. 
On the Estimation of Phosphoric Acid as Pyrophosphate of Magnesia. 
- By T. R. Oetrvie. 
On a Sesquisulphide of Iron. By Dr. T. L. Putrsoy, F.C.S. 
This is a substance of a beautiful dark emerald-green colour, having the compo- 
sition Fe? Cl?, which is. produced when ferric chloride is added to a solution of 
ammonia sulphide containing a considerable amount of hypochlorite of soda, or 
whenever a persalt of iron containing free chlorine or a hypochlorite is precipi- 
tated by sulphide of ammonium. 
It forms a dark green flocculent precipitate, appearing quite black when collected 
and washed. Its fine green colour becomes apparent when, after drying, it is 
ground up with a perfectly white powder such as chalk. 
Its properties are rather remarkable. It is soluble to a notable extent in water 
containing ammonia, and separates therefrom as the ammonia escapes; it is even 
soluble in alcoholic ammonia, forming in each case a bright emerald-green solution. 
It is only slightly soluble in a mixture of sulphide and hypochlorite rather diluted ; 
neither is it more than slightly soluble in either of these alone. It is more easily 
dissolved in hot water containing free ammonia. 
In hydrochloric acid it dissolves with great effervescence, immediately producing 
perchloride of iron, Fe? Cl’, in spite of the abundance of sulphuretted hydrogen 
resent. 
On analysis it is proved to be a hydrated sesquisulphide of iron, answering very 
nearly to the formula 2Fe? S*+-3HO. 
On the Presence of Cyanogen in Commercial Bromine, and a means of 
detecting it. By Dr. T. L. Putrson, FCS. 
- The author has lately discovered a notable amount of cyanogen in samples of 
bromine supposed to be pure and issued as such for pharmaceutical purposes. It 
has been long known that during the manufacture of iodine a certain quantity of 
that beautiful but dangerous compound todide of cyanogen sometimes finds its way 
into one of the glass condensers ; and from the fact just alluded to it would appear 
that a similar compound with bromine may occasionally be produced during the , 
manufacture of this liquid element ; this is a more serious case than the other, since 
the impurity is dissolved and hidden in the liquid. 
The presence of cyanogen in bromine may be detected by taking an equal weight 
of iron filings to that of the bromine to be examined, adding to them four or five 
times their weight of water and mixing in the bromine gradually, stirring all the 
time. The liquid must be filtered while warm from the reaction, and the filtrate 
allowed to stand in a partially closed bottle; in the course of about twenty-four 
hours a precipitate of ferricyanide of iron (Berlin blue) will have formed, and may 
be collected on a filter. 
If perfectly pure bromine were used this reaction would also enable us to detect 
cyanogen in steel, and to decide whether or no it is ever present in that metal. 
Notes on the Preparation of the Sulphur-wrea. By Prof. Emerson Rerynotps. 
On the Action of the Sulphur-urea in Metallic Solutions. 
By Professor Emerson Rrynoxps. 
On a Self-registering Apparatus for Measuring the Chemical Action of Laght. 
By Professor Roscoz, FAS. 
