摘要:

294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected.The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results.The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.

ISSN:0003-2654    

DOI:10.1039/AN9325700485

出版商:RSC    

年代:1932

数据来源: RSC

摘要:

486 OBITUARY CECIL HOWARD CRIBB Obituary CECIL HOWARD CRIBB THE announcement of the death of Cecil H. Cribb in the July issue of THE ANALYST must have been read by his many friends with great regret. On June 11th Cribb was taken seriously ill and despite an operation he passed away on the 13th. He was 68 years of age. By his death the Society loses one of its most ardent supporters for after his election as a Member in January 1890 Cribb took a very deep interest in the affairs of the Society. From 1895 onwards he served on different occasions as a Member of Council and also for two periods as a Vice-President. Since 1908 he served on the Publication Committee of THE ANALYST, the interests of our journal being dear to him and up to the last month he read the proofs with unfailing assiduity and attended the prolonged meetings of the Committee with unflagging zeal.He was also greatly interested in the work of the Institute of Chemistry and was the first Examiner (1907-1911) in the Chemistry of Foods and Drugs under the scheme of examinations introduced during the Presidency of Professor P. F. Frankland. He received his early education at a boarding school at Leatherhead and at University College School and about 1878 proceeded to the School of Mines South Kensington where he studied under T. H. Huxley and Sir Edward Frankland, among others. For nearly two years he acted as assistant to Professor Purdie at St. Andrews University where his manipulative skill and ingenuity proved valuable in devising lecture experiments. Afterwards he became assistant to Professor P.F. Frankland. In 1887 he registered as a medical student at University College Hospital and covered a large part of a medical course though he never qualified. In the early eighties he opened a laboratory in London and commenced practice as an analytical chemist and this practice he carried on until his death. His first public appointment was that of Public Analyst to the Strand Board of Works (1886) and in those early days if the food samples submitted were few in number they provided a very considerable amount of work owing to widespread adulteration. When the Strand became incorporated in the City of Westminster, Cribb became a joint Public Analyst for that City. The other important public appointment which he held was that of Public Analyst for the Metropolitan Borough of Fulham.During the nineties he took part in collaboration with H. H. F. Hyndman in experiments on the then recently discovered X-rays. His private practice was considerable in extent and included the examination of a number of waters for he was consulting analyst to several Water Companies. The late hour to which he stayed in his laboratory every evening is a proof of his zeal for work and those who had the privilege of working with him can testify to his ability and to his versatile brain. He revelled in attacking a difficult problem and many days or even weeks would pass before his ingenious mind would exhaust phases of work which might yield the desired result. Cribb will long be remembered for his resourcefulness in introducing new forms of chemical apparatus.Probably he is best known as the inventor of the double-surface condenser. It might well be said that until Cribb attacked th OBITUARY CECIL HOWARD CRIBB 487 methods used for the condensation of vapours in the laboratory the Liebig condenser or a worm condenser were accepted as irreplaceable pieces of apparatus. Condensers a foot or a yard in length were reverenced and few people had even thought that any other form of condenser was possible or permissible in a laboratory. Cribb really showed that a 4-inch upright condenser could work as efficiently as many feet of glass tubing surrounded with water. Commercially he met with a similar difficulty that of convincing anyone that there was any apparatus that could work as efficiently as the old type of condenser.His carbon dioxide apparatus is familiar to many. This apparatus and his specific gravity bottle have features which should have made them even more popular than they have become. However his ingenuity was by no means restricted to devising apparatus for use in the laboratory for many other conceptions were the subject of patents taken out by him. During the cycle craze about 1897 he invented a bicycle head which by easy treatment could be made to lock the steering of a cycle This device was actually purchased by a cycle company. Then an automatic machine for the delivery of postage stamps received his attention but the device was in advance of public opinion or possibly requirements. In 1900 Cribb published a paper on “The Influence of Temperature and Pressure on the Saline Constituents of Boiler Water.” This paper showed the decomposition of various salts which occurs when waters are concentrated under pressure etc.Papers then followed describing the new forms of carbonic acid apparatus, and also the double-surface condenser mentioned above. In 1905 the results of an investigation carried out in conjunction with another investigator were published showing the action of slightly alkaline waters on iron. Papers written in conjunction with others were published later on “A Method for the Approximate Determination of Boric Acid,’’ “ Analyses of Cream Cheese,” “The Facing of Rice,” “The Analysis of Margarine,” and a very important contribution at that date “ The Composition and Analysis of Chocolate.” He was joint author with H.Mansfield Robinson of the book “Law and Chemistry of Foods and Drugs.” Cribb was an enthusiastic collector of antiques and of old prints chiefly relative to chemistry and he acquired a very considerable knowledge of these. His collection of prints of the alchemists and their laboratories was very large and representative and he also possessed many pieces of old scientific apparatus. Though never of robust constitution he spared himself no physical effort; in fact he had a great belief in exercise and for many years he cycled between his old home at East Finchley and his laboratory in the West End of London. Only the recent crowded state of the thoroughfares and his health made him forsake his cycle for the train. He was devoted to dogs having a predilection for the largest breeds. A man of broad outlook a deep thinker a scientist with a gift of easy con-versation-how all who knew him must miss him! The sadness of his old friends at his graveside was a token of the deep affection of his fellow men for him and the presence of so many was an appreciation of the services he so unstintingly rendered to the profession. F. W. F. ARNAUD His recreations included cycling lawn tennis and gardening

ISSN:0003-2654    

DOI:10.1039/AN9325700486

出版商:RSC    

年代:1932

数据来源: RSC

摘要:

488 DODD CASTOR SEED IN FEEDING STUFFS Castor Seed in Feeding Stuffs BY F. ROBERTSON DODD F.I.C. (Extract from a paper rend at the Meeting of the North of England Section, February 13 1932) OPINIONS are divided as to the desirability of stating definitely the quantity of castor which may be present in a feeding stuff or of fixing any limit which must not be exceeded. Dr. Voelcker Chemist to the Royal Agricultural Society, regards the giving of percentage figures for castor seed present as being utterly misleading owing to the uneven distribution of the castor. He accordingly declines altogether to certify to percentages present but condemns a food as unfit for use if he finds castor in it. Force of circumstances however compels most of us who handle the raw materials as they enter the country to state the percentages, since the new contracts specify limits.For the County Analyst who receives a much smaller sample than we a t the ports of entry any trace of castor seed should be sufficient to condemn tl-and there should be no need for him to state quantities. When the controversy arose some years ago my late partner suggested to the trade that a limit of 0.005 per cent. of castor seed should be fixed but Liverpool merchants regarded this limit as too risky and agreed to insert in the contract a clause to the effect that if any one of three analysts found any trace of castor seed, the buyer could reject the parcel. An unwritten opinion is current that any quantity of castor seed over 0.01 per cent. may prove fatal to cattle.This so far as I know is without foundation, beyond the fact that castor poisoning has occurred when no analyst has found more than 0.02 per cent. Owing to rumours which circulate in the business world the question is now being asked whether there is a difference in the toxicity of various species of castor seed. This rumour is persistent and does not lack the support of certain chemists. “Some castor seeds may be harmless,’’ says the rumour, “whilst others may be deadly.” To my mind there is only one course open to the County Analyst namely to regard all castor seeds as deadly and to report accordingly. While the general details of the method for the detection of castor seeds are, doubtless familiar to most there may yet be some points gathered by me in a lengthy experience which may be found useful.My own laboratory generally receives a sample of 7 to 10 lbs. in weight. This is broken into small pieces and quartered down the quartered portion being passed through a mill which reduces it to pass a sieve with ten meshes to the inch. This ground portion is passed through a Clarkson sampling machine and the portion delivered is weighed and used for one test. The process is repeated on the portion of the original sample first broken down until four samples of 50 to 120 grms. have been obtained. DODD CASTOR SEED IN FEEDING STUFFS 489 In doubtful cases further portions are prepared and treated. Certain analysts weigh 1 lb. of the sample and use that for their test but I prefer to prepare a number of samples in the way described the total quantity being generally between 250 and 500grms.The portions selected are treated with 500 C.C. of dilute sulphuric acid (1.25 per cent.) and then after being washed by decantation with 300 C.C. dilute sodium hydroxide solution (1.25 per cent.). The washing after the treatment with sodium hydroxide may be very important. In such materials as kapok seed cake for example the colouring matter is very difficult to remove and interferes with subsequent bleaching. A solution of calcium hypochloride sufficient to bring the liquor in which the fibres are suspended to a strength of approximately 1 per cent. of “available” chloride is added and the mixture stirred frequently during the bleaching process. Castor Croton For linseed cakes the fibres of which are easily bleached half the above strength of hypochlorite suffices.Last year certain “ Russian’’ linseed cake contained a rather high percentage of castor seed which bleached readily under ordinary conditions. Whether this was immature seed or not I cannot say; I merely record my experience. At the end of that time the sample is washed by decantation and spread out on a white dish, and the black particles are picked out and examined under the microscope. Finally the residue is washed quickly with dilute hydrochloric acid to remove the last traces of hypochlorite and then with water and again picked over to recover any pieces of husk which have escaped the former search. Certain foreign makers have lately been grinding seed much more finely than formerly for the extraction of the oil and the castor-seed husk is so comminuted that it may occur in very minute particles which are difficult to see and separate.As a rule the bleaching process should not occupy more than an hour 490 DODD CASTOR SEED I N FEEDING STUFFS Identification under the microscope is at present the subject of adverse criticism by shippers who accuse English chemists of incompetence and several of us have had letters stating that we have mistaken mustard or hemp seeds for castor. The seeds which might easily be mistaken for castor include grape or raisin seed and ucuhuba seed (possibly) both of which are harmless; croton seed and curcas seed both more poisonous than castor. It is usual to return castor croton or curcas as castor seed.Ucuhuba seed presents little difficulty but grape seed often presents a real difficulty. Often one finds on the inner side of grape-seed husk a membrane not unlike a finger print which is never found on castor-seed husk but more often there is little except the size of the “pin holes” to distinguish the two. I am referring to the blackened grape seed from wine-making processes not to the light seeds which bleach well. Grape Curcas Palisade cells and upper surface view The black grape husks picked out when treated with sulphurous acid turn purple fairly quickly whilst the castor husks remain black for a long time. If the husks be treated with 50 C.C. of N / 2 hydrochloric acid and 4 grms. of potassium chlorate on a water-oven for about an hour the palisade cells separate, and can be examined under a Q in.objective when there need remain no doubt in the mind of the observer. The diagrams drawn with the aid of a camera lucida by a former assistant, Mr. 0. A. Morch slightly exaggerate the points to be looked for. The photographs taken by my assistants Messrs. Telford and Waters explain themselves. The magnifications are approximately 40 and 140. As a closing note I may add that, when stating percentages the system adopted in Germany is now generally required i.e. the London contracts have copied the German rule of stating the percentage of castor-seed husk found. The chemical treatment to which a meal is subjected before picking out the husks extracts from castor-seed husk substances amounting to one-fifth of its weight i.e.80 per cent. only is found 1 3 2 4 5 6 (1) Castor x 140 (5) Grape X 40. (2) Curcas Palisade cells x 140 (3) Croton x 140 (4) Grape x 140 Husks with top-light illumination Mixed fibres (0) Castor and Grape x 40 DODD CASTOR SEED IN FEEDING STUFFS 491 The custom based on the average fibre content of castor seeds is to weigh the husk found and multiply this weight by 5 to express the percentage of seed. The weight of the husk increased by one-fourth should represent the castor-seed husk originally present. An alternative method is to multiply the weight of the husk by 5 (= castor seed) and to divide this result by 4 (= castor-seed husk originally present). (See also J. W. Leather ANALYST 1892 17 121; Lander and Geake id., 1914,39 292; Brioux and Guerbet id.1921,46 100; H. Waites id. 1922,47 306; Report of Case id. 1932 381.) DISCUSSION The PRESIDENT welcomed Mr. E. E. Billington not onlyas a member of the Society but also as a manufacturer who could present the manufacturers’ view to the meeting. Mr. BILLINGTON joined issue with Mr. Dodd on the statement that analysts should condemn feeding stuffs if they contained a minute trace of castor seed. He had experimented i r the feeding of cattle with cakes containing 0.001 per cent. 01 castor seed without in efiects. He gave details of several cases of castor-seed poisoning which had been investigated and contended that the analyst was not merely a detective and judge combined but one to whom the community looked to investigate such subjects and to suggest measures to counteract the effects of the poison.The introduction of small quantities of castor seed into feeding stuffs was never intentional and so far as chemical control on arrival a t Liverpool and in reputable works was concerned every attempt was made to prevent its inclusion. Other feeding stuffs could be substituted for pea nlit (arachis) meal but these would affect the fat of the milk and particularly the character of the butter made therefrom and manufacturers wishful to do their best for their customers were compelled by monetary considerations to use the best available materials. In spite of the most rigorous control traces of castor seed occasionally found their way into the products and in cases where the total quantity present was very minute, he thought that the analyst should be merciful in his report.With regard to the acceptance by continental importers of parcels which this country had rejected, there was another reason than that given by Mr. Dodd. By the time the chemist’s report was issued showing that castor seed was present the consignment was in barges many miles away and the expense of bringing it back and re-delivering it to the sellers would be so great that buyers accepted delivery bztt demanded an allowance. Professor W. H. ROBERTS drew attention to the fact that cattle could be immunised to castor seed. Mr. J. HANLEY confirmed this and mentioned the different reactions of various animals to the poison. Some of his experiments (made under licence) had shown that whilst one animal died from consuming a mixture containing castor seed others not only showed no ill effects but throve on the mixture.The difficulty was that when a number of animals were fed on beans and one of the animals promptly died one could not decide whether it was a case of poisoning or of idiosyncrasy of the animal. He instanced also a case of human idiosyncrasy of an assistant who within half-an-hour of chewing beans of uqknown origin (which he did not swallow) developed a red rash all over his body. The rash did not disappear for a few days. Mr. S. E. MELLING asked whether in view of its well-known de-toxicating properties active carbon had ever been tried on animals suffering from the poison; if not he suggested that such treatment was worthy of consideration 492 EVANS AN IMPROVED METHOD OF TITRATING ARSENIC Mr. A. R. TANKARD mentioned that during the war investigations made in Hull on behalf of the Ministry of Agriculture and Fisheries had shown that it was possible to treat castor seed in such a way as to render the meal quite innocuous to live stock. He asked whether it was possible to apply any simple method to distinguish such treated meal from the actively poisonous material. A general discussion followed in which questions as to the action of the lipase or enzyme; the occurrence of castor seed in various materials; the effect on workers with castor seeds etc. were mooted. Messrs. Dodd and Billington received the thanks of the meeting for their valuable contributions to the discussion

ISSN:0003-2654    

DOI:10.1039/AN9325700488

出版商:RSC    

年代:1932

数据来源: RSC

摘要:

294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected.The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results.The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable.The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm.Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected.Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm.in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic.This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm.of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased.The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.

ISSN:0003-2654    

DOI:10.1039/AN9325700492

出版商:RSC    

年代:1932

数据来源: RSC

摘要:

294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected.The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results.The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable.The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm.Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected.Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm.in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic.This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm.of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased.The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm.up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation.Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity.CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C.of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view.Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned.Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium.Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms.of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.

ISSN:0003-2654    

DOI:10.1039/AN9325700495

出版商:RSC    

年代:1932

数据来源: RSC

摘要:

294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected.The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results.The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable.The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm.Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected.Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm.in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic.This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm.of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased.The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm.up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation.Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity.CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C.of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view.Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned.Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium.Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms.of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view.Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium.Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C.of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm.in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable.The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm.of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased.The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms.give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation.Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium.Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased.The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm.up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes.Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium.Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline.Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present.Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms.of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C.of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide.A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable.The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm.Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected.Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C.the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic.This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters.It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.

ISSN:0003-2654    

DOI:10.1039/AN9325700500

出版商:RSC    

年代:1932

数据来源: RSC

摘要:

294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected.The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results.The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable.The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm.Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected.Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm.in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic.This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm.of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased.The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm.up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation.Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity.CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C.of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.

ISSN:0003-2654    

DOI:10.1039/AN9325700511

出版商:RSC    

年代:1932

数据来源: RSC

摘要:

514 NOTES Notes The Editor wishes to point out that the pages of the Journal are open f o r the inclusion Such notes of short notes dealing with analytical practice and kindred matters. are submitted to the Publication Committee in tlae usual manner. THE USE OF ULTRA-VIOLET LIGHT FOR THE DETECTION OF TRACES OF SULPHITES AT the suggestion of Mr. J. A. Radley we have made a series of experiments on the detection of sulphites by oxidation to sulphuric acid and formation of the fluorescent quinine sulphate. A boiling-tube was fitted with a tap-funnel and an outlet consisting of an inverted U-tube with a bulb blown in each leg. This delivered into a test-tube immersed in cold water and containing 5 C.C. of boiled distilled water and 1 C.C. (or less) of the purest hydrogen peroxide (40 vol.) obtainable.About 10 C.C. of a solution containing known amounts of potassium sulphite were measured into the boiling-tube sufficient 50 per cent. hydrochloric acid to acidify the mixture was added through the tap-funnel and the whole was boiled gently so as to distil over 2 or 3 C.C. of water. The contents of the test-tube were then shaken well with a speck of quinine and examined in filtered ultra-violet light when the presence of 0-25 mgrm. or more of sulphur dioxide was indicated by the brilliant violet fluorescence of quinine sulphate. The only disadvantage of the method is the great sensitiveness of the fluorescence reaction. In the first place it is extremely difficult to obtain a sample of hydrogen peroxide or of bromine water which does not itself fluoresce with quinine and for this reason the minimum quantity of the former must be used.Secondly care must be taken that no spray reaches the test-tube during the distillation. Attempts to increase the sensitiveness by adding powdered .calciu NOTES 515 carbonate to the acid solution so as to produce a non-oxidising atmosphere of carbon dioxide were not successful as a fluorescence was obtained without addition of sulphite. When phosphoric acid was used in place of hydrochloric acid high blanks were again obtained and it should be noted that quinine phosphate also fluoresces in filtered ultra-violet light. The blank fluorescence obtained under the experimental conditions recommended above is however too weak to be confused with that from 0.25 mgrm.of SO,. JULIUS GRANT J. H. W. BOOTH HACKNEY TECHNICAL INSTITUTE, LONDON SANDALWOOD AND ITS SUBSTITUTES THE two photomicrographs reproduced in the February issue of THE ANALYST (p. 124) representing tangential longitudinal sections of sandalwood and kalamet wood respectively do not show with sufficient clearness the structures intended, Sandalwood (Santalum album) Kalamet Wood (Mansonia Gagei) Tangential longitudinal Sections magnified x 50 lin. The accompanying photomicrographs taken at a higher magnification ( x SO), show the storage rays more clearly. It will be seen that the rays (viz. the lenticular, porous zones) of kalamet wood (Mansonia Gagei) are arranged in tiers or stories, which appear to the naked eye or when examined with a hand-lens as “ripple marks.” These form a feature of specific diagnostic value in certain woods and may be seen on polished longitudinal sections as fine parallel lines; the average number per inch is worth recording for any given species.It should be noted that in true sandalwood (Santalum album) on the other hand the rays possess no such definite arrangement. In the last line of the original note “Fig. 3” should read “Fig. 4.” 3 RAWLINSON ROAD OXFORD J. CECIL MAB 516 NOTES POISONING BY CARBON MONOXIDE FROM A GAS-HEATER ON December 19th 1931 a man and woman aged 25 and 49 respectively were seen about 5 a.m. by the man’s brother who slept in a room leading out of their room. He thought at that time that nothing was wrong and it was not until 11 a.m. that on passing through the room a second time his suspicions were aroused and he informed the police and the man and woman who were unconscious, were taken to a hospital.On both occasions when he passed through the room he had noticed that the man was lying in bed and that the woman was in a sitting position on the floor. The woman died after a known period of unconsciousness of about 24 hours. The man recovered after a period of unconsciousness of about 36 hours. The former was deeply unconscious all the time but in the latter unconsciousness was light. Clinically except for slight cyanosis dilated but reacting pupils an irregular feeble pulse and the fact that the man had vomited prior to admission there was no evidence of poisoning but the taking of a narcotic poison was presumed.The post-mortem findings in the case of the woman were quite negative as was also the analysis of the viscera. The blood of the woman contained no carbon monoxide. A small bottle of tablets of two kinds (aspirin and potassium chlorate) was found in the room. The man on recovery denied that there was a suicide pact or that he had taken poison. He could not account in any way for what had happened and remembered nothing after getting into bed. He was living he said happily and was in regular work. In view of the negative findings an enquiry was made about coal-gas poisoning. The brother who had passed through the room had smelt nothing and the police found the gas-taps in order and the gas-meter was of a quarterlyvariety. When the police arrived a small gas-stove was burning in the room; it was subsequently elicited that the occupants of the room were not in the habit of leaving the stove burning all night.At this time some six weeks after the tragedy I requested that the gas-stove should be sent to me. It had been sold and after some difficulty was found by the police in a second-hand dealer’s shop and was sent to me. I further elicited the fact that it was not connected with the chimney in the room and that the regulator of the chimney was closed so that all fumes from the burning stove must have been discharged into the room. The gas-stove was of a very old-fashioned pattern and one which might be expected to produce carbon monoxide. The room occupied by these persons was 13 ft. 3 in. by 11 ft. 4 in. by 8 ft. It had two doors one of which was closed and the other open to the width of a crack and one window which was closed except for a quarter of an inch a t the toy.The bed was between the stove and the door leading to the second room which was also the one open the width of a crack. The man was found lying on the side of the bed nearer to the slightly open door and the woman was found on the floor on the opposite side of the bed i.e. away from the slightly open door. I arranged for the stove to be sent to the Government Chemist and his report, based on work done by Mr. L. C. Nickolls of that department is most interesting, and is here given in detail. REPORT OF THE GOVERNMENT CHEMIST.-“ The gas-heater has been tested under varying conditions of gas consumption and air supply.“When the heater is burning its maximum quantity of from 10 to 12 cubic feet of gas per hour the amount of carbon monoxide in the products of combustion is approximately 2 parts in 10,000 equivalent to 20 parts in 10,000 of the gas No poison was detected in the vomit of the man NOTES 517 burned and the equilibrium concentration in the air of the room (13 f t . 3 in. x 11 ft. 4 in. x 8 ft. = 1200 cb. ft.) is: Assuming 4 air-change 1 air-change per hour per hour 0.5 0.25 2 air-changes per hour 0.1 part in 10,000 “ These concentrations of carbon monoxide are innocuous. Similarly when the gas supply to the heater is reduced to 5 cubic feet an hour no increase in the quantity of carbon monoxide produced is observed. When however the gas supply is maintained at about 8 cubic feet per hour a critical condition exists in the behaviour of the heater and irrespective of alterations in the air supply, relatively very large quantities of carbon monoxide are produced and dangerous concentrations in the air of the room might be obtained.“ I n one experiment the exit gases from the heater contained 71 parts in 10,000 of carbon monoxide (equivalent to 1780 parts in 10,000 of the gas burned), and the equilibrium concentration in the above room would be: Assuming 4 air-change 1 air-change 2 air-changes per hour per hour per hour 24 12 6 parts in 10,000 “The two former concentrations are lethal the last after some hours’ exposure might prove lethal. “The probable number of air changes an hour in the room in question is based upon the following considerations:-In the first report of the Departmental Committee to enquire into the ventilation of factories and workshops 1902 (Appendix 11 p.105) it is stated that in small rooms having all apertures closed the ventilation varies from 4 to 2 air-changes an hour while the Director of the Building Research Station Uepartment of Scientific and Industrial Research has reported that the air-changes in a closed room may vary from 4 to 1Q an hour.” Efect of Carbon Mu~zoxide.-If about one-half of the blood is unavailable for carrying oxygen (i.e. 50 per cent. saturation with carbon monoxide) the patient will be seriously ill but if removed from the vitiated atmosphere will recover in many instances. If however such a saturation is maintained in his blood for a period of hours it follows that during this time sufficient oxygen is not reaching the body particularly the brain with the result that the latter becomes damaged.Although the patient when removed from the vitiated atmosphere rids himself of the carbon monoxide the damage which has already taken place to the brain-cells is such that unconsciousness persists and the patient may die This distinction is important as the person who puts his head in a gas-oven for example, and dies in a few minutes dies directly from the effects of poisoning by carbon monoxide. Evidence of Carbon Monoxide Poisoning on Arrival of the Patients at the Hospital.-According to the times given to me about two hours elapsed between the calling of the police and the arrival at the hospital.As soon as patients are removed from the influence of carbon monoxide by ventilation of the room or by being taken into the open air the concentration of carbon monoxide in the blood rapidly diminishes and no doubt when the patients arrived at the hospital there was no clinical evidence of poisoning. It is stated that carbon monoxide can disappear from the blood in 30 minutes in fresh air. Long Period of Unconsciousness in Hospital.-In rapidly fatal cases of carbon monoxide poisoning death is due directly to the gas. In the cases in question saturation was slow and never reached a very high level but exposure was of considerable length. Death was probably due to damage to the brain cells from this long exposure. In the case of the man the damage was less serious, so recovery ensued 518 OFFICIAL APPOINTMENTS Recovery of the Man and Death of the Woman.-The position of the man in bed that is to say nearer the slightly open door suggests that some ventilation in the form of incoming currents of air resulted in his receiving a lower concentration of carbon monoxide in the air that he breathed so that the percentage saturation in his blood was less.This is supported by the fact that when the police found him he was not fully unconscious. The position of the woman was very charac-teristic (“the woman herself being in a sitting position on the floor ”). No doubt she realised at some time during the night that the stove was still burning and attempted to get out of bed to extinguish it. When persons are partly under the influence of carbon monoxide the slightest muscular effort e.g.getting out of bed, is accompanied by great breathlessness resulting in the inhaling of still more carbon monoxide and great muscular weakness. As soon as she got out of bed, she immediately collapsed on the floor and found herself unable to move. As she was well away from the window and the door the concentration of carbon monoxide reached a higher level in her blood than in that of the man so that when found, she was fully unconscious and during the time which elapsed between the gassing and the giving of the alarm the percentage saturation in her blood was maintained a t a sufficiently high level to produce ultimately a fatal result. History of the Exposwe.-Assuming that the stove was lit about midnight and that the patients were first seen about 5 to 6 a.m.there had been from 6 to 6 hours’ exposure. The brother then walked through the room and no doubt caused some temporary ventilation. The two persons were then exposed for another 5 hours. As the concentration in the room for the first few hours that the stove was burning would be very low it may be assumed that they had about 7 hours of effective exposure to a noxious concentration of carbon monoxide in the air of the room. When the blood is about 25 per cent. saturated with carbon monoxide the first symptoms appear; at 30 to 35 per cent. definite symptoms such as increased breathing muscular weakness giddiness etc. occur; at 50 per cent. the symptoms become urgent; at 50 to 60 per cent. unconsciousness supervenes; and a t 65 to 85 per cent. death will occur. In the case of the man the highest percentage reached in the blood was probably about 50 per cent. and for the woman the percentage was rather higher. Breathing 15 to 20 parts of carbon monoxide in the air per 10,000 parts can cause death in 4 hours and upwards that is to say, at 65 to 85 per cent. saturation. In these cases I suggested that about 50 per cent. saturation occurred and that it was maintained for about 7 hours. Therefore it is fair to assume that the concentration in the air of the room was for most of the time considerably less than 15 parts per 10,000 of carbon monoxide. From the report of the Government Chemist it is evident that even with 1 air-change per hour the concentrations I postulated in the blood of these people could easily have been attained. G. ROCHE LYNCH DEPARTMENT OF CHEMICAL PATHOLOGY, ST. MARY’S HOSPITAL, LONDON W.

ISSN:0003-2654    

DOI:10.1039/AN9325700514

出版商:RSC    

年代:1932

数据来源: RSC

摘要:

294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected.The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results.The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable.The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm.Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected. The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected.Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results. The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm.in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.

ISSN:0003-2654    

DOI:10.1039/AN9325700518

出版商:RSC    

年代:1932

数据来源: RSC

摘要:

294 EVERS: THE DETECTION OF SMALL QUANTITIES OF CALCIUM Adding 5 mgrms. of calcium. Added salts. Result. No added salt. Immediate pptn. Sodium chloride, 1 grm. Borax, 1 grm. Sodium potassium tartrate, 1 grm. Potassium citrate, 1 grm. Variations in the concentration of the reagents did not appreciably improve matters. It was found that even 0.25 grm. of potassium citrate in 60 C.C. of solution prevented the precipitation of 2 mgrms. of calcium. Further complications would be introduced if magnesium were also present in the salt as an impurity. CALCIUM OLEATE TEsT.-The formation of an opalescence on the addition of sodium oleate solution to a solution is an extremely delicate test for calcium. Under the best conditions 0.01 mgrm. of calcium in 50 C.C. of solution, or 0.00002 per cent., can just be detected.The test is also, of course, a test for magnesium, but is much less sensitive, 0-6 mgrm. in 50 C.C. of solution, or 0-0012 per cent., being the minimum quantity which can be detected. Further, within certain limits of concentration the pre- cipitation of magnesium is entirely suppressed in the presence of potassium citrate, whilst the sensitiveness of the calcium test is actually increased. The best conditions for the detection of calcium were found to be as follows: Take 50 C.C. of the solution containing calcium, which should be neutral or slightly alkaline. Dissolve in it 2 grms. of potassium citrate, and add 0-3 C.C. of a solution prepared by dissolving 10 grms. of oleic acid in 200 C.C. of 1 per cent. sodium hydroxide. A certain excess of alkali is desirable for the best results.The test is only satisfactory between certain limits of calcium concentration. With quantities exceeding 1 mgrm. in 60 C.C. the opalescence is actually reduced. Under the above conditions quantities of mag- nesium up to 15 mgrms. give no opalescence. Summarising the results, the oleate test is excellent for quantities of calcium varying from 0-01 mgrm. up to 1 mgrm. in the absence of more than 10 mgrms. of magnesium, and within these limits in the absence of other salts the opalescence appears proportional to the calcium present. Further experiments showed, however, that, in spite of its delicacy, the oleate test is not suitable for the purpose in view. Possibly, if the test could be carried out, using standards containing the same concentration of the same salt, it would be satisfactory, but this is hardly practicable. The addition of other salts, even in the absence of potassium citrate, caused the results to be erratic. This was partly due to their “salting out ” effect on the soap, which sometimes caused flocculation, but this was not the whole explanation. Almost immediate pptn. Slight ppt. after 30 minutes. Slight ppt. after 30 minutes. No ppt. This line of investigation was therefore abandoned. Mix and allow the mixture to stand. An excess of the reagent gives less opalescence.

ISSN:0003-2654    

DOI:10.1039/AN9325700519

出版商:RSC    

年代:1932

数据来源: RSC