THE ANALYST.. 98 CORRESPONDENCE. [The Editors are not responsible for the opinions of their Correspondents.] To THE EDITOR OF ‘‘ THE ANALYST.” SIR,-AS I was not present on the 15th January last, when the discussion took place on my note on the “ Influence of Age on the Composition of Butter Fat,” I shall be glad to reply by a letter in your columns, more especially as the criticisms were very far from flattering.Dr. Dupr6 says it was ‘‘ unfortunate ” I had published two analyses of some of the butters ; now I think some of your readers who may have read my three contributions on the subject may not be of the same opinion, and I will try to show why I claim exemption from deserving Dr. DuprB’s severe strictures. I think it must be admitted that I clearly show how the figures forming the tables in my first paper were arrived at, the amount of washing, &c., &c., and this paper raised perhaps only two original questions : 1st.Are not the “ Insoluble Acids ” generally somewhat higher than stated by Dr. DuprB? 2ndly. Did volatility in the air-bath account for the lower results? At any rate, these were the only two points questioned in the discussion, and I most willingly admit that both, i.e., my higher ‘‘ insoluble acids ” and observed volatility were suggeated as being accounted for by the extent of the washing ; this I doubted at the time, and hence the experiments communicated in my second note, which went against my opinion, and proved the conjectures of my friends correct, Now, it is certainly more gratifying to find one’s opinion confirmed, yet I cannot recognise any ‘ 6 great moral courage ” in admitting and showing its confutation ; but, observe, I simply admit an error of opinion as to the action of further zoaehing.I by no means accept the extended washing as desirable, leading as it does to an extra loss in the analysis ; only about a third of the bodies so extracted being estimated with soda on the factor in use, and my opinion is still what I expressed at the end of my second note, that I consider the analyses in my first paper show the more correct constitution of butter fat than if the washing be extended.The term ‘‘ insoluble ” can only be applied here in a comparative sense to indicate practical insolubility in water : for continual washing will produce continual diminition to some degree.Washing beyond the extent mentioned in my first paper, which gives a total filtrate of about 600 c.c., extrads only about 6 milligrammes per 100 C.C. I therefore think such extended washing is not worth pursuing, especially as it is mainly lost in the analysis by being reckoned on the factor for butyric acid. The results shown in my third paper of the analyses of the butter fat, after keeping the butters, I say are strictly comparable with the first analyses, being, as there stated, conducted in exaotly the same way with the same washing.How then is the table thrown out and made useless, as stated by Dr. Dupr6 ? The exact niodus operandi is known, the amount of washing is stated, and the effect of extended washing, if any one prefers to pursue it, can be calculated from the second paper.I have not and do not admit the “ insoluble aoids ” in my first paper to be incorrect, and cannot see Dr. DuprB’s authority for stating it. Respecting the results in my third paper, I will only say that there is no mistake about the irregularity of the character of the changes either as to specific gravity or cmstitution of the fat as to soluble and insoluble acids.Yours truly, Wolverhampton, Mu~ch 26th, 1879. E. W. T. JONES. To THE EDITOR OF ‘‘ THE ANLYST.” SIR,-The following notes on the permanganate process of Professbr Tidy imy bc welcome to tjome of your readers :- A permanganate solution was prepared in accordance with his directions on the 3rd of last March ; a large clean crystal of hyposulphite was selected, powdered, dhed in blotting paper, and the necessary quantity weighed off for the standard solution ; 64 septems were required to destroy the blue colour of the iodine in the experiment conducted at the commencement of the three hours ; exactly the same quantity was requisite after one hour, and after three hours.The flasks were in moderate daylight.Repeated experiments have since shown, that under these circumstances, no change whatever takcs place in the weak a c i ~ e d solution of permanganate in distilled water during the period required for one of Tidy’s determinations. On the 20th of March the same solution of permanganate was titrated for another purpose, with freshly prepared decinormd oxalio acid ; ten grain measures, very carefully taken, required 8.2 O.C.of permanganat e .94 THE ANALYST. On the 28th of March the solution was again titrated with ‘‘ hypo.” selected, powdered, and dried as before ; 53 septems of hypo. solution were required. On the 10th of April (this morning) the aolution waa again examined as before, with both ‘‘ hypo.” and decinormal O X ~ ~ C acid ; 53 septems of hypo.solution were required for the 20 septems taken as usual, and ten grain measures of the oxalic acid were oxidized by 8.3 C.C. The “hypo.” was in each case taken from the same batch. It would appear, therefore, that a solution of permanganate of Tidy’s strength can be depended upon for at least a month, at the average temperature of a laboratory in the spring (from 40° to 559 F.).It should be mentioned that the solution which forms the subject of this letter was jealously excluded from the light, and I am of opinion that the commonly accepted idea of the extreme instability of weak permanganate solutions is to be traced to a neglect of this precaution. Since the appearance of Professor Tidy’s paper I have been in the habit of working water analyses in duplicate, by his process and that of Wanklyn, and the impression left on my mind by the limited experience I have had at present is, that, if the latter process be carried out exactly in accordance with the directions of ita author, the agreement in the conclusions to be drawn from the reeultr; of the two methocls will be much closer than it was found to be by Tidy, when working with his considerably modified form of the ammonia process.Shrewsbury, April loth, 1879. Yours, &c., THOS. P. BLUNT, M.A., Oxox., F.C.S. To TEE EDITOR OF ‘‘ THE ANALYST.” Sm,-We observe in THE ANALYST for this month, there is a report of a paper read by Dr. Duprit, before the Society of Public Analysts, upon violet powder, in which the Steamer Over a Globe ” Violet Powder is prominently mentioned. Passing over the fallacies and the erroneous conclusions* contained in the paper, and the questionable proceeding of actually enumerating arsenic, amongst the constituents of different varieties of violet powder, in estimating their respective merits ; to prevent any misunderstanding, we wish to state distinctly as a fact, that the solitary conviction at Lambeth, for selling violet powder, which appears to be Dr.Duprb’s only crumb of comfort on this question, did not refer to our “ Steamer Over a Globe” Violet Powder, or it would have been immediately appealed against ; but, that when that invincible article was brought before the same magistrate, on April 2nd last, after hearing evidence on both sides, Mr. Chance pronounced this Violet Powder uninjurious, that there wag no official formula for violet powder, hence it could not be said to be aditerated ; he dismissed the summons, and also another against a different maker, thus virtually cancelling his former adverse decision, and leaving the article practically victorious in every case. We enclose our card, and remain yours, &c., Tm MANUFACTURERS OF THE “STEAMER OVER A GLOBE” VIOLET POWDER. [* The writers omit to point out what are the fallacies and errone )us conclusions to which they allude. -ED. ANALYST.]