238 



SCmNGE. 



[N. S. Vol. VIII. No. 191. 



being for all values of n equal to 2, as in the 

 case of water.* 



The study of the complex acids which 

 contain ortho-phosphoric acid as such 

 naturally led to that of complex acids con- 

 taining other acids of phosphorus. The 

 greater number, or at least the more im- 

 portant, of these have been shown to give 

 well-defined complex acids, and in all cases 

 appeared to contain the phosphorus com- 

 pound in the modification in which it ex- 

 isted before the combination with tungstic 

 or molybdic oxide. Since this work was 

 completed several new acids containing 

 phosphorus have been discovered, more 

 especially the so-called hypo-phosphoric 

 acid, and it is to be hoped that these also 

 will be studied from the same point of view. 

 I shall ask attention to the compounds now 

 known. The only pyrophospho-tungstates 

 yet observed belong to the general types for 

 the acids 



(22W03.9P,0,H,) 2E0. 

 and for the salts 



(22W03.9P,0,R,.) 2110. 



The salts containing molybdic teroxide 

 differ from the above and belong to difier- 

 ent types. All those which were examined 

 contained manganous oxide and all con- 

 tained but two molecules of pyrophosphoric 

 acid or corresponding pyrophosphates in 

 place of nine. It is not easy to see how the 

 presence of manganous oxide as base can 

 affect the formation of such salts, but the 

 analyses of a pyrophospho-tungstate con- 

 taining six molecules of manganous oxide 

 correspond very closely to a formula em- 

 braced under the type 



I4WO3.6RO + P,0,RV 



so that, so far as the empirical constitution 

 is concerned, the salt may be regarded as 

 double and as containing two salts belong- 

 ing to well known types. In the present 

 *See American Journal of Science and jdWs, Vol. 

 XLIV., November, 1867. 



state of our knowledge it seems more prob- 

 able that the pyrophospho-tungstates and 

 pyrophospho-molybdates are double salts 

 belonging to the second class of complex 

 inorganic salts. The solutions of the alka- 

 line salts give, with solutions of the heavy 

 metals, precipitates which contain only 

 pyrophosphoric acid and neither tungsten 

 nor molybdenum. On the other hand, it is 

 well worthy of notice that the group 



9(P,0,E,) 



is capable of existing independently of 

 tungstic oxide. Wallroth has shown that 

 we have salts of the type 



(P.O,),R"io^e,,. 



Of the other modifications of phosphoric 

 acid I shall notice only the mono-metaphos- 

 phates and the hexa-metaphosphates. In 

 the case of the former the type of the tung- 

 sten compounds is : 



(mW03.2P03R)pR'0. 



As in the case of the pyrophospho-tung- 

 states we have here to distinguish an inter- 

 nal and an external basicity, the group 

 (mW03.2P03E.) standing in the relation of a 

 complex oxide to the external group pK'O. 

 For the mono-meta-phosphomolybdates the 

 type is different : 



(m'Mo034P03R)p'R'0 



and, of course, other types are possible. So 

 far as we can now judge the salts contain- 

 ing mono-meta-phosphoric acid belong to 

 the first group like phosphotungstates and 

 phosphomolybdates of the type 



12W03.PO,R3 and 12Mo03PO,R3. 



They give no reactions characteristic of 

 their constituents,but the precipitates which 

 they form with metallic salts have the oily 

 or pasty character of the salts of metaphos- 

 phoric acid. 



The only hexa-metaphosphomolybdate 

 examined has the formula 



