Analytical data are presented, which have been collected over a period of years (1925-48), for the purpose of aiding in the determination of the fruit content of fruit products.Analytical results for various fruits with which one is commonly concerned in the analysis of fruit products were published by Hughes and Maunselll in 1934, together with details of the use of the non-sugar solids value, as an aid in the calculation of the fruit content of such products as jams, pulps, canned fruits, etc. Particular reference was made to the use of a statistical quantity designated the " probable minimum non-sugar solids." * Thc fruit content calculated

18MONEY et a1.-ANALYTICAL DATA O F COMMON FRUITS panels regarded the blocks with desiccant after 12 months' storage a t 37" as equal in quality to those without desiccant after only z months (possibly 3, but no sample was taken at 3 months). In the case of uncompressed material, that with desiccant was shown still to be of good quality a t the end of the experimental period of 14 months a t 37O. The uncompressed product without desiccant remained a t this level of quality for only z (possibly 3) months. Against these prolongations of stored life must be set a reduction of about 5% in the loose material that can be packed into a can, and a reduction of 20% in the quantity of compressed material, and also the cost of the desiccant and its container, and the additional labour required for handling thc desiccant.

As a result of studies of the equilibrium humidity‐concentration relationship of a number of solutions of sugars, an empirical formula has been derived relating the equilibrium humidity value with the molar concentration. The equation is of the same form as that derived from Raoult's law, but is applicable over a wide range of concentrations. An ‘equivalent molecular weight’ has been derived for the solids of glucose syrup, whereby this material may be considered in a similar manner to simple sugars. Examples are given of the application of the equation in the calculation of the equilibrium humidity values of jams, fondant creams and boiled sweets.

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Comparative rests were carried out on the purification of crude pectin esmcts by (a) dialysis, (b) precipitation by alcohol, and (c) ionic exchange. The results showed that dialysis followed by precipitation gave the highest calcium pectate value and complete removal of sugars, free acids and free ash. Ionic exchange gave a pectin of considerably lower residual ash content, but the additional reduction was at the espcnse of the inorganic ions combined with the pectin and is thus of doubtful desirability, except for particular purposes.The present conception of the pectin molecule is of a long chain molecule of galacturonic acid units, esterified to a greater or less extent, and " pectin " emacted from the plant material a n be regarded as a mixture of such chains of various lengths. The definition of a " pure " pectin is thus a relative term and involves such questions as, for example (u) whether or not pectin is chemically inert during extraction ; (6) is it justifiable to speak of pectin as an entity ? (c) do pectins from different species of plants vary? (d) is the pectin from ripe fruit the same as pectin from unripe fruit from the same species, etc.? Consideration of the various studies that have been reported indicates that, in many cases, the results obtained can only be regarded as indicative of the composition of the particular sample under consideration, for the reason that the purity of the material is open to criticism. It is obvious that for a fundamental study the presence of adventitious substances, such as sugars, salt and acids, must be obviated as far as possible and that criteria must be established as to what constitutes " pure " pectin and to recognise the limitations of the interpretation of the analytical results. "Pectin I' is normally determined by hydrolysis to pectic acid, precipitating and weighing the insoluble calcium salt, the procedure employed being the classical method of Card and Haynest or one of the modifications of this method j other methods of deternlination by weighing the precipitate obtained on the addition of alcohol or acetone appear to lack the specific character of the calcium pectate method in relation to pectic substances as defined above. Further characterisation of " pectin " is afforded by the carboy1 groups (which as stated above are esterified to a greater or less extent) ; the total of such groups, when expressed as the equivalent sodium hydroxide, should be theoretically 22.8% of the pectic acid, or 20.5% of the equivalent calcium pectate. Thus reasonable criteria of the purity of a particular " pectin " are the approach of the calcium pectate value* to 10oq/O and the approach of the total carboxyl groups (i.e., the sum of the free acidic groups, those estcrified and those combined with inorganic ions, all expressed in terms of the equivalent sodium hydroxide) to 20.5% of this value. Methods of purification considered(I) Precipifafiorr.-The method normally employed for the separation of " pectin " from a crude extract is to precipitate the pectin from an aqu...