551 
On the Food of Plaitts. 
Quan titaiive A n alijsis. 
10 grains of" ash lost nothing by ignition. 
Treated with li3'clrochloric acid and fiUered, left of unburnt 
charcoal and sandy matter ..... 0'9 grains. 
Solution mixed with ammonia and filtered ; phosphates 
weighed after ignition . . . . . . 3*7 „ 
Hence the ash contained — 
Phosphates of magnesia and lime . . . 3'7 
Sandy matter, &c. . . . . . 0'9 
Alkaline phosphate by difference . . .5*4 
10-0 
The vahie of an analysis made in such a manner depends altogether 
on the care with which the qualitative examination has been made, and 
the absence of all other substances completely established. The diffi- 
culty of obtaining a sufficient quantity of material to work upon is a 
great bar to any more elaborate investigations ; the simplicity of the ash, 
however, renders these needless. 
When the soluble part of an ash contains carbonate, sulphate, and 
phosphate, an exact analysis becomes very difficult. I have in such 
cases contented myself with determining the two latter by precipitation, 
by baryta, and taking the carbonate by difference. Perhaps it would be 
as well to check this result by determining directly the carbonic acid, 
which could easily be done, and the quantity of alkali by its saturating 
power, if great accuracy were required. 
I have assumed the composition of phosphate, of baryta, precipitated 
by excess of ammonia, to be represented by the formula — 
5 Ba O + 2 P O5 (Berzelius). 
The determination of the quantity of potash in a mixture of a salt of 
that base with one of soda presents no difficulty. The salt is converted 
into a chloride by means which need not be here described ; a portion is 
then placed in a platinum crucible, gently ignited, and its weight ascer- 
tained ; it is next dissolved in a little water, and mixed with four times 
its weight of the double chloride of ]ilatinum and sodium in crystals; 
when the decomposition is complete, alcohol is added, and the insoluble 
yellow salt placed upon a weighed filter, washed with dilute alcohol, 
dried at 212° and weighed. From the weight of this, the double chloride 
of platinum and potassium, it is easy to calculate the quantity of chloride 
of potassium which it contains. 
On the Delerrnination of Gluten in Grain. 
The method which has hitherto been usually had recourse to for this 
purpose consists in making the meal to be examined into a paste with 
cold water, and kneading it in the hand in a little stream of water until 
the latter is no longer rendered milky by the separated starch ; in the 
beginning of the operation the paste is inclosed in a piece of rag, but 
towards the end it is usual to retain it in the palm of the hand without 
any envelope. When it is thought that the washing has been conducted 
