Dr. Playfair on the Nitropriissides. 197 



to arise from the first term of (1.) of the first paper, and to 



be of the form — g (a + ^sin^t;); but as they are multiplied by 



small quantities in the values of Dg, Dg, we may neglect the 

 part of r depending on e. A constant resulting from integra- 

 tion should be added, and may be supposed to be included. 

 We may therefore change in (18.) Dg into D2 + w^ sin^t;, or Kg 

 into Kg + wsin^i;, Dg being now constant, and make 



7n — E2 cos 2^2== Lg. 

 Then we must change Gg into 



2 + ofu ^'" ^'^^ sm^i;. 

 Thus we may replace (18.) by 



F2= Kg + L2 sin^tJ— - Eg sin^o sin 2^2 sin 2z + S^Eg cos 2^2 



cos (2— tt) + ^^Eg sin 2^2 sin {z—ii), 

 /Sgzs G2 + N2 sin^u— - H2 sin^o sin2— 2eH2sin {z—it) 



Here — j=2. has been made equal to 



and we have 



p + q snirv 

 2D2 ' 



G2=^2-^sin2^2 + ^: N2=(l-h^)^sin2^2+4. 



'2 -^-^2 



Gunthwaite Hall, near Barnsley, Yorkshire, 

 February 4, 1850. 



[To be continued.] 



XXVII. On the Nitroprussides, a New Class of Salts. 

 By Dr. Lyon Playfair, F.R.S., F.C.S.* 

 1 ,TN an inquiry into the constitution of the prussides, I found 

 A it necessary to examine into the somewhat anomalous 

 action of nitric acid on the yellow prusside of potassium. This 

 examination has led to the discovery of a singular class of 

 compounds, which form the subject of the present memoir. 



The previous knowledge on the action of nitric acid on the 

 prussides may be summed up very briefly. Thomson* ex- 

 amined the gases produced during the action, and recognized 



* From the Philosophical Transactions for 1849, part ii. ; having been 

 received by the Royal Society June 21, and read June 21 , 1849. 

 t As quoted by Gmelin, Handbuch, vol. iv. p. 370. 



